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9e7543e939
kernel_optimize_test/fs/namei.c
Al Viro 9e7543e939 remove incorrect comment in lookup_one_len() 
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-04-11 22:24:30 -04:00

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/*
* linux/fs/namei.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*/
/*
* Some corrections by tytso.
*/
/* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname
* lookup logic.
*/
/* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture.
*/
#include <linux/init.h>
#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/namei.h>
#include <linux/pagemap.h>
#include <linux/fsnotify.h>
#include <linux/personality.h>
#include <linux/security.h>
#include <linux/ima.h>
#include <linux/syscalls.h>
#include <linux/mount.h>
#include <linux/audit.h>
#include <linux/capability.h>
#include <linux/file.h>
#include <linux/fcntl.h>
#include <linux/device_cgroup.h>
#include <linux/fs_struct.h>
#include <linux/posix_acl.h>
#include <linux/hash.h>
#include <asm/uaccess.h>
#include "internal.h"
#include "mount.h"
/* [Feb-1997 T. Schoebel-Theuer]
* Fundamental changes in the pathname lookup mechanisms (namei)
* were necessary because of omirr. The reason is that omirr needs
* to know the _real_ pathname, not the user-supplied one, in case
* of symlinks (and also when transname replacements occur).
*
* The new code replaces the old recursive symlink resolution with
* an iterative one (in case of non-nested symlink chains). It does
* this with calls to <fs>_follow_link().
* As a side effect, dir_namei(), _namei() and follow_link() are now
* replaced with a single function lookup_dentry() that can handle all
* the special cases of the former code.
*
* With the new dcache, the pathname is stored at each inode, at least as
* long as the refcount of the inode is positive. As a side effect, the
* size of the dcache depends on the inode cache and thus is dynamic.
*
* [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
* resolution to correspond with current state of the code.
*
* Note that the symlink resolution is not *completely* iterative.
* There is still a significant amount of tail- and mid- recursion in
* the algorithm. Also, note that <fs>_readlink() is not used in
* lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
* may return different results than <fs>_follow_link(). Many virtual
* filesystems (including /proc) exhibit this behavior.
*/
/* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
* New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
* and the name already exists in form of a symlink, try to create the new
* name indicated by the symlink. The old code always complained that the
* name already exists, due to not following the symlink even if its target
* is nonexistent. The new semantics affects also mknod() and link() when
* the name is a symlink pointing to a non-existent name.
*
* I don't know which semantics is the right one, since I have no access
* to standards. But I found by trial that HP-UX 9.0 has the full "new"
* semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
* "old" one. Personally, I think the new semantics is much more logical.
* Note that "ln old new" where "new" is a symlink pointing to a non-existing
* file does succeed in both HP-UX and SunOs, but not in Solaris
* and in the old Linux semantics.
*/
/* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
* semantics. See the comments in "open_namei" and "do_link" below.
*
* [10-Sep-98 Alan Modra] Another symlink change.
*/
/* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
* inside the path - always follow.
* in the last component in creation/removal/renaming - never follow.
* if LOOKUP_FOLLOW passed - follow.
* if the pathname has trailing slashes - follow.
* otherwise - don't follow.
* (applied in that order).
*
* [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
* restored for 2.4. This is the last surviving part of old 4.2BSD bug.
* During the 2.4 we need to fix the userland stuff depending on it -
* hopefully we will be able to get rid of that wart in 2.5. So far only
* XEmacs seems to be relying on it...
*/
/*
* [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
* implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
* any extra contention...
*/
/* In order to reduce some races, while at the same time doing additional
* checking and hopefully speeding things up, we copy filenames to the
* kernel data space before using them..
*
* POSIX.1 2.4: an empty pathname is invalid (ENOENT).
* PATH_MAX includes the nul terminator --RR.
*/
#define EMBEDDED_NAME_MAX (PATH_MAX - offsetof(struct filename, iname))
struct filename *
getname_flags(const char __user *filename, int flags, int *empty)
{
struct filename *result;
char *kname;
int len;
result = audit_reusename(filename);
if (result)
return result;
result = __getname();
if (unlikely(!result))
return ERR_PTR(-ENOMEM);
/*
* First, try to embed the struct filename inside the names_cache
* allocation
*/
kname = (char *)result->iname;
result->name = kname;
len = strncpy_from_user(kname, filename, EMBEDDED_NAME_MAX);
if (unlikely(len < 0)) {
__putname(result);
return ERR_PTR(len);
}
/*
* Uh-oh. We have a name that's approaching PATH_MAX. Allocate a
* separate struct filename so we can dedicate the entire
* names_cache allocation for the pathname, and re-do the copy from
* userland.
*/
if (unlikely(len == EMBEDDED_NAME_MAX)) {
const size_t size = offsetof(struct filename, iname[1]);
kname = (char *)result;
/*
* size is chosen that way we to guarantee that
* result->iname[0] is within the same object and that
* kname can't be equal to result->iname, no matter what.
*/
result = kzalloc(size, GFP_KERNEL);
if (unlikely(!result)) {
__putname(kname);
return ERR_PTR(-ENOMEM);
}
result->name = kname;
len = strncpy_from_user(kname, filename, PATH_MAX);
if (unlikely(len < 0)) {
__putname(kname);
kfree(result);
return ERR_PTR(len);
}
if (unlikely(len == PATH_MAX)) {
__putname(kname);
kfree(result);
return ERR_PTR(-ENAMETOOLONG);
}
}
result->refcnt = 1;
/* The empty path is special. */
if (unlikely(!len)) {
if (empty)
*empty = 1;
if (!(flags & LOOKUP_EMPTY)) {
putname(result);
return ERR_PTR(-ENOENT);
}
}
result->uptr = filename;
result->aname = NULL;
audit_getname(result);
return result;
}
struct filename *
getname(const char __user * filename)
{
return getname_flags(filename, 0, NULL);
}
struct filename *
getname_kernel(const char * filename)
{
struct filename *result;
int len = strlen(filename) + 1;
result = __getname();
if (unlikely(!result))
return ERR_PTR(-ENOMEM);
if (len <= EMBEDDED_NAME_MAX) {
result->name = (char *)result->iname;
} else if (len <= PATH_MAX) {
struct filename *tmp;
tmp = kmalloc(sizeof(*tmp), GFP_KERNEL);
if (unlikely(!tmp)) {
__putname(result);
return ERR_PTR(-ENOMEM);
}
tmp->name = (char *)result;
result = tmp;
} else {
__putname(result);
return ERR_PTR(-ENAMETOOLONG);
}
memcpy((char *)result->name, filename, len);
result->uptr = NULL;
result->aname = NULL;
result->refcnt = 1;
audit_getname(result);
return result;
}
void putname(struct filename *name)
{
BUG_ON(name->refcnt <= 0);
if (--name->refcnt > 0)
return;
if (name->name != name->iname) {
__putname(name->name);
kfree(name);
} else
__putname(name);
}
static int check_acl(struct inode *inode, int mask)
{
#ifdef CONFIG_FS_POSIX_ACL
struct posix_acl *acl;
if (mask & MAY_NOT_BLOCK) {
acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS);
if (!acl)
return -EAGAIN;
/* no ->get_acl() calls in RCU mode... */
if (acl == ACL_NOT_CACHED)
return -ECHILD;
return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK);
}
acl = get_acl(inode, ACL_TYPE_ACCESS);
if (IS_ERR(acl))
return PTR_ERR(acl);
if (acl) {
int error = posix_acl_permission(inode, acl, mask);
posix_acl_release(acl);
return error;
}
#endif
return -EAGAIN;
}
/*
* This does the basic permission checking
*/
static int acl_permission_check(struct inode *inode, int mask)
{
unsigned int mode = inode->i_mode;
if (likely(uid_eq(current_fsuid(), inode->i_uid)))
mode >>= 6;
else {
if (IS_POSIXACL(inode) && (mode & S_IRWXG)) {
int error = check_acl(inode, mask);
if (error != -EAGAIN)
return error;
}
if (in_group_p(inode->i_gid))
mode >>= 3;
}
/*
* If the DACs are ok we don't need any capability check.
*/
if ((mask & ~mode & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0)
return 0;
return -EACCES;
}
/**
* generic_permission - check for access rights on a Posix-like filesystem
* @inode: inode to check access rights for
* @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
*
* Used to check for read/write/execute permissions on a file.
* We use "fsuid" for this, letting us set arbitrary permissions
* for filesystem access without changing the "normal" uids which
* are used for other things.
*
* generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
* request cannot be satisfied (eg. requires blocking or too much complexity).
* It would then be called again in ref-walk mode.
*/
int generic_permission(struct inode *inode, int mask)
{
int ret;
/*
* Do the basic permission checks.
*/
ret = acl_permission_check(inode, mask);
if (ret != -EACCES)
return ret;
if (S_ISDIR(inode->i_mode)) {
/* DACs are overridable for directories */
if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE))
return 0;
if (!(mask & MAY_WRITE))
if (capable_wrt_inode_uidgid(inode,
CAP_DAC_READ_SEARCH))
return 0;
return -EACCES;
}
/*
* Read/write DACs are always overridable.
* Executable DACs are overridable when there is
* at least one exec bit set.
*/
if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO))
if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE))
return 0;
/*
* Searching includes executable on directories, else just read.
*/
mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
if (mask == MAY_READ)
if (capable_wrt_inode_uidgid(inode, CAP_DAC_READ_SEARCH))
return 0;
return -EACCES;
}
EXPORT_SYMBOL(generic_permission);
/*
* We _really_ want to just do "generic_permission()" without
* even looking at the inode->i_op values. So we keep a cache
* flag in inode->i_opflags, that says "this has not special
* permission function, use the fast case".
*/
static inline int do_inode_permission(struct inode *inode, int mask)
{
if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) {
if (likely(inode->i_op->permission))
return inode->i_op->permission(inode, mask);
/* This gets set once for the inode lifetime */
spin_lock(&inode->i_lock);
inode->i_opflags |= IOP_FASTPERM;
spin_unlock(&inode->i_lock);
}
return generic_permission(inode, mask);
}
/**
* __inode_permission - Check for access rights to a given inode
* @inode: Inode to check permission on
* @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
*
* Check for read/write/execute permissions on an inode.
*
* When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
*
* This does not check for a read-only file system. You probably want
* inode_permission().
*/
int __inode_permission(struct inode *inode, int mask)
{
int retval;
if (unlikely(mask & MAY_WRITE)) {
/*
* Nobody gets write access to an immutable file.
*/
if (IS_IMMUTABLE(inode))
return -EACCES;
}
retval = do_inode_permission(inode, mask);
if (retval)
return retval;
retval = devcgroup_inode_permission(inode, mask);
if (retval)
return retval;
return security_inode_permission(inode, mask);
}
EXPORT_SYMBOL(__inode_permission);
/**
* sb_permission - Check superblock-level permissions
* @sb: Superblock of inode to check permission on
* @inode: Inode to check permission on
* @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
*
* Separate out file-system wide checks from inode-specific permission checks.
*/
static int sb_permission(struct super_block *sb, struct inode *inode, int mask)
{
if (unlikely(mask & MAY_WRITE)) {
umode_t mode = inode->i_mode;
/* Nobody gets write access to a read-only fs. */
if ((sb->s_flags & MS_RDONLY) &&
(S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
return -EROFS;
}
return 0;
}
/**
* inode_permission - Check for access rights to a given inode
* @inode: Inode to check permission on
* @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
*
* Check for read/write/execute permissions on an inode. We use fs[ug]id for
* this, letting us set arbitrary permissions for filesystem access without
* changing the "normal" UIDs which are used for other things.
*
* When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
*/
int inode_permission(struct inode *inode, int mask)
{
int retval;
retval = sb_permission(inode->i_sb, inode, mask);
if (retval)
return retval;
return __inode_permission(inode, mask);
}
EXPORT_SYMBOL(inode_permission);
/**
* path_get - get a reference to a path
* @path: path to get the reference to
*
* Given a path increment the reference count to the dentry and the vfsmount.
*/
void path_get(const struct path *path)
{
mntget(path->mnt);
dget(path->dentry);
}
EXPORT_SYMBOL(path_get);
/**
* path_put - put a reference to a path
* @path: path to put the reference to
*
* Given a path decrement the reference count to the dentry and the vfsmount.
*/
void path_put(const struct path *path)
{
dput(path->dentry);
mntput(path->mnt);
}
EXPORT_SYMBOL(path_put);
struct nameidata {
struct path path;
struct qstr last;
struct path root;
struct inode *inode; /* path.dentry.d_inode */
unsigned int flags;
unsigned seq, m_seq;
int last_type;
unsigned depth;
struct file *base;
char *saved_names[MAX_NESTED_LINKS + 1];
};
/*
* Path walking has 2 modes, rcu-walk and ref-walk (see
* Documentation/filesystems/path-lookup.txt). In situations when we can't
* continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
* normal reference counts on dentries and vfsmounts to transition to rcu-walk
* mode. Refcounts are grabbed at the last known good point before rcu-walk
* got stuck, so ref-walk may continue from there. If this is not successful
* (eg. a seqcount has changed), then failure is returned and it's up to caller
* to restart the path walk from the beginning in ref-walk mode.
*/
/**
* unlazy_walk - try to switch to ref-walk mode.
* @nd: nameidata pathwalk data
* @dentry: child of nd->path.dentry or NULL
* Returns: 0 on success, -ECHILD on failure
*
* unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry
* for ref-walk mode. @dentry must be a path found by a do_lookup call on
* @nd or NULL. Must be called from rcu-walk context.
*/
static int unlazy_walk(struct nameidata *nd, struct dentry *dentry)
{
struct fs_struct *fs = current->fs;
struct dentry *parent = nd->path.dentry;
BUG_ON(!(nd->flags & LOOKUP_RCU));
/*
* After legitimizing the bastards, terminate_walk()
* will do the right thing for non-RCU mode, and all our
* subsequent exit cases should rcu_read_unlock()
* before returning. Do vfsmount first; if dentry
* can't be legitimized, just set nd->path.dentry to NULL
* and rely on dput(NULL) being a no-op.
*/
if (!legitimize_mnt(nd->path.mnt, nd->m_seq))
return -ECHILD;
nd->flags &= ~LOOKUP_RCU;
if (!lockref_get_not_dead(&parent->d_lockref)) {
nd->path.dentry = NULL;
goto out;
}
/*
* For a negative lookup, the lookup sequence point is the parents
* sequence point, and it only needs to revalidate the parent dentry.
*
* For a positive lookup, we need to move both the parent and the
* dentry from the RCU domain to be properly refcounted. And the
* sequence number in the dentry validates *both* dentry counters,
* since we checked the sequence number of the parent after we got
* the child sequence number. So we know the parent must still
* be valid if the child sequence number is still valid.
*/
if (!dentry) {
if (read_seqcount_retry(&parent->d_seq, nd->seq))
goto out;
BUG_ON(nd->inode != parent->d_inode);
} else {
if (!lockref_get_not_dead(&dentry->d_lockref))
goto out;
if (read_seqcount_retry(&dentry->d_seq, nd->seq))
goto drop_dentry;
}
/*
* Sequence counts matched. Now make sure that the root is
* still valid and get it if required.
*/
if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
spin_lock(&fs->lock);
if (nd->root.mnt != fs->root.mnt || nd->root.dentry != fs->root.dentry)
goto unlock_and_drop_dentry;
path_get(&nd->root);
spin_unlock(&fs->lock);
}
rcu_read_unlock();
return 0;
unlock_and_drop_dentry:
spin_unlock(&fs->lock);
drop_dentry:
rcu_read_unlock();
dput(dentry);
goto drop_root_mnt;
out:
rcu_read_unlock();
drop_root_mnt:
if (!(nd->flags & LOOKUP_ROOT))
nd->root.mnt = NULL;
return -ECHILD;
}
static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
{
return dentry->d_op->d_revalidate(dentry, flags);
}
/**
* complete_walk - successful completion of path walk
* @nd: pointer nameidata
*
* If we had been in RCU mode, drop out of it and legitimize nd->path.
* Revalidate the final result, unless we'd already done that during
* the path walk or the filesystem doesn't ask for it. Return 0 on
* success, -error on failure. In case of failure caller does not
* need to drop nd->path.
*/
static int complete_walk(struct nameidata *nd)
{
struct dentry *dentry = nd->path.dentry;
int status;
if (nd->flags & LOOKUP_RCU) {
nd->flags &= ~LOOKUP_RCU;
if (!(nd->flags & LOOKUP_ROOT))
nd->root.mnt = NULL;
if (!legitimize_mnt(nd->path.mnt, nd->m_seq)) {
rcu_read_unlock();
return -ECHILD;
}
if (unlikely(!lockref_get_not_dead(&dentry->d_lockref))) {
rcu_read_unlock();
mntput(nd->path.mnt);
return -ECHILD;
}
if (read_seqcount_retry(&dentry->d_seq, nd->seq)) {
rcu_read_unlock();
dput(dentry);
mntput(nd->path.mnt);
return -ECHILD;
}
rcu_read_unlock();
}
if (likely(!(nd->flags & LOOKUP_JUMPED)))
return 0;
if (likely(!(dentry->d_flags & DCACHE_OP_WEAK_REVALIDATE)))
return 0;
status = dentry->d_op->d_weak_revalidate(dentry, nd->flags);
if (status > 0)
return 0;
if (!status)
status = -ESTALE;
path_put(&nd->path);
return status;
}
static __always_inline void set_root(struct nameidata *nd)
{
get_fs_root(current->fs, &nd->root);
}
static int link_path_walk(const char *, struct nameidata *);
static __always_inline unsigned set_root_rcu(struct nameidata *nd)
{
struct fs_struct *fs = current->fs;
unsigned seq, res;
do {
seq = read_seqcount_begin(&fs->seq);
nd->root = fs->root;
res = __read_seqcount_begin(&nd->root.dentry->d_seq);
} while (read_seqcount_retry(&fs->seq, seq));
return res;
}
static void path_put_conditional(struct path *path, struct nameidata *nd)
{
dput(path->dentry);
if (path->mnt != nd->path.mnt)
mntput(path->mnt);
}
static inline void path_to_nameidata(const struct path *path,
struct nameidata *nd)
{
if (!(nd->flags & LOOKUP_RCU)) {
dput(nd->path.dentry);
if (nd->path.mnt != path->mnt)
mntput(nd->path.mnt);
}
nd->path.mnt = path->mnt;
nd->path.dentry = path->dentry;
}
/*
* Helper to directly jump to a known parsed path from ->follow_link,
* caller must have taken a reference to path beforehand.
*/
void nd_jump_link(struct nameidata *nd, struct path *path)
{
path_put(&nd->path);
nd->path = *path;
nd->inode = nd->path.dentry->d_inode;
nd->flags |= LOOKUP_JUMPED;
}
void nd_set_link(struct nameidata *nd, char *path)
{
nd->saved_names[nd->depth] = path;
}
EXPORT_SYMBOL(nd_set_link);
char *nd_get_link(struct nameidata *nd)
{
return nd->saved_names[nd->depth];
}
EXPORT_SYMBOL(nd_get_link);
static inline void put_link(struct nameidata *nd, struct path *link, void *cookie)
{
struct inode *inode = link->dentry->d_inode;
if (inode->i_op->put_link)
inode->i_op->put_link(link->dentry, nd, cookie);
path_put(link);
}
int sysctl_protected_symlinks __read_mostly = 0;
int sysctl_protected_hardlinks __read_mostly = 0;
/**
* may_follow_link - Check symlink following for unsafe situations
* @link: The path of the symlink
* @nd: nameidata pathwalk data
*
* In the case of the sysctl_protected_symlinks sysctl being enabled,
* CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is
* in a sticky world-writable directory. This is to protect privileged
* processes from failing races against path names that may change out
* from under them by way of other users creating malicious symlinks.
* It will permit symlinks to be followed only when outside a sticky
* world-writable directory, or when the uid of the symlink and follower
* match, or when the directory owner matches the symlink's owner.
*
* Returns 0 if following the symlink is allowed, -ve on error.
*/
static inline int may_follow_link(struct path *link, struct nameidata *nd)
{
const struct inode *inode;
const struct inode *parent;
if (!sysctl_protected_symlinks)
return 0;
/* Allowed if owner and follower match. */
inode = link->dentry->d_inode;
if (uid_eq(current_cred()->fsuid, inode->i_uid))
return 0;
/* Allowed if parent directory not sticky and world-writable. */
parent = nd->path.dentry->d_inode;
if ((parent->i_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH))
return 0;
/* Allowed if parent directory and link owner match. */
if (uid_eq(parent->i_uid, inode->i_uid))
return 0;
audit_log_link_denied("follow_link", link);
path_put_conditional(link, nd);
path_put(&nd->path);
return -EACCES;
}
/**
* safe_hardlink_source - Check for safe hardlink conditions
* @inode: the source inode to hardlink from
*
* Return false if at least one of the following conditions:
* - inode is not a regular file
* - inode is setuid
* - inode is setgid and group-exec
* - access failure for read and write
*
* Otherwise returns true.
*/
static bool safe_hardlink_source(struct inode *inode)
{
umode_t mode = inode->i_mode;
/* Special files should not get pinned to the filesystem. */
if (!S_ISREG(mode))
return false;
/* Setuid files should not get pinned to the filesystem. */
if (mode & S_ISUID)
return false;
/* Executable setgid files should not get pinned to the filesystem. */
if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP))
return false;
/* Hardlinking to unreadable or unwritable sources is dangerous. */
if (inode_permission(inode, MAY_READ | MAY_WRITE))
return false;
return true;
}
/**
* may_linkat - Check permissions for creating a hardlink
* @link: the source to hardlink from
*
* Block hardlink when all of:
* - sysctl_protected_hardlinks enabled
* - fsuid does not match inode
* - hardlink source is unsafe (see safe_hardlink_source() above)
* - not CAP_FOWNER
*
* Returns 0 if successful, -ve on error.
*/
static int may_linkat(struct path *link)
{
const struct cred *cred;
struct inode *inode;
if (!sysctl_protected_hardlinks)
return 0;
cred = current_cred();
inode = link->dentry->d_inode;
/* Source inode owner (or CAP_FOWNER) can hardlink all they like,
* otherwise, it must be a safe source.
*/
if (uid_eq(cred->fsuid, inode->i_uid) || safe_hardlink_source(inode) ||
capable(CAP_FOWNER))
return 0;
audit_log_link_denied("linkat", link);
return -EPERM;
}
static __always_inline int
follow_link(struct path *link, struct nameidata *nd, void **p)
{
struct dentry *dentry = link->dentry;
int error;
char *s;
BUG_ON(nd->flags & LOOKUP_RCU);
if (link->mnt == nd->path.mnt)
mntget(link->mnt);
error = -ELOOP;
if (unlikely(current->total_link_count >= 40))
goto out_put_nd_path;
cond_resched();
current->total_link_count++;
touch_atime(link);
nd_set_link(nd, NULL);
error = security_inode_follow_link(link->dentry, nd);
if (error)
goto out_put_nd_path;
nd->last_type = LAST_BIND;
*p = dentry->d_inode->i_op->follow_link(dentry, nd);
error = PTR_ERR(*p);
if (IS_ERR(*p))
goto out_put_nd_path;
error = 0;
s = nd_get_link(nd);
if (s) {
if (unlikely(IS_ERR(s))) {
path_put(&nd->path);
put_link(nd, link, *p);
return PTR_ERR(s);
}
if (*s == '/') {
if (!nd->root.mnt)
set_root(nd);
path_put(&nd->path);
nd->path = nd->root;
path_get(&nd->root);
nd->flags |= LOOKUP_JUMPED;
}
nd->inode = nd->path.dentry->d_inode;
error = link_path_walk(s, nd);
if (unlikely(error))
put_link(nd, link, *p);
}
return error;
out_put_nd_path:
*p = NULL;
path_put(&nd->path);
path_put(link);
return error;
}
static int follow_up_rcu(struct path *path)
{
struct mount *mnt = real_mount(path->mnt);
struct mount *parent;
struct dentry *mountpoint;
parent = mnt->mnt_parent;
if (&parent->mnt == path->mnt)
return 0;
mountpoint = mnt->mnt_mountpoint;
path->dentry = mountpoint;
path->mnt = &parent->mnt;
return 1;
}
/*
* follow_up - Find the mountpoint of path's vfsmount
*
* Given a path, find the mountpoint of its source file system.
* Replace @path with the path of the mountpoint in the parent mount.
* Up is towards /.
*
* Return 1 if we went up a level and 0 if we were already at the
* root.
*/
int follow_up(struct path *path)
{
struct mount *mnt = real_mount(path->mnt);
struct mount *parent;
struct dentry *mountpoint;
read_seqlock_excl(&mount_lock);
parent = mnt->mnt_parent;
if (parent == mnt) {
read_sequnlock_excl(&mount_lock);
return 0;
}
mntget(&parent->mnt);
mountpoint = dget(mnt->mnt_mountpoint);
read_sequnlock_excl(&mount_lock);
dput(path->dentry);
path->dentry = mountpoint;
mntput(path->mnt);
path->mnt = &parent->mnt;
return 1;
}
EXPORT_SYMBOL(follow_up);
/*
* Perform an automount
* - return -EISDIR to tell follow_managed() to stop and return the path we
* were called with.
*/
static int follow_automount(struct path *path, unsigned flags,
bool *need_mntput)
{
struct vfsmount *mnt;
int err;
if (!path->dentry->d_op || !path->dentry->d_op->d_automount)
return -EREMOTE;
/* We don't want to mount if someone's just doing a stat -
* unless they're stat'ing a directory and appended a '/' to
* the name.
*
* We do, however, want to mount if someone wants to open or
* create a file of any type under the mountpoint, wants to
* traverse through the mountpoint or wants to open the
* mounted directory. Also, autofs may mark negative dentries
* as being automount points. These will need the attentions
* of the daemon to instantiate them before they can be used.
*/
if (!(flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) &&
path->dentry->d_inode)
return -EISDIR;
current->total_link_count++;
if (current->total_link_count >= 40)
return -ELOOP;
mnt = path->dentry->d_op->d_automount(path);
if (IS_ERR(mnt)) {
/*
* The filesystem is allowed to return -EISDIR here to indicate
* it doesn't want to automount. For instance, autofs would do
* this so that its userspace daemon can mount on this dentry.
*
* However, we can only permit this if it's a terminal point in
* the path being looked up; if it wasn't then the remainder of
* the path is inaccessible and we should say so.
*/
if (PTR_ERR(mnt) == -EISDIR && (flags & LOOKUP_PARENT))
return -EREMOTE;
return PTR_ERR(mnt);
}
if (!mnt) /* mount collision */
return 0;
if (!*need_mntput) {
/* lock_mount() may release path->mnt on error */
mntget(path->mnt);
*need_mntput = true;
}
err = finish_automount(mnt, path);
switch (err) {
case -EBUSY:
/* Someone else made a mount here whilst we were busy */
return 0;
case 0:
path_put(path);
path->mnt = mnt;
path->dentry = dget(mnt->mnt_root);
return 0;
default:
return err;
}
}
/*
* Handle a dentry that is managed in some way.
* - Flagged for transit management (autofs)
* - Flagged as mountpoint
* - Flagged as automount point
*
* This may only be called in refwalk mode.
*
* Serialization is taken care of in namespace.c
*/
static int follow_managed(struct path *path, unsigned flags)
{
struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */
unsigned managed;
bool need_mntput = false;
int ret = 0;
/* Given that we're not holding a lock here, we retain the value in a
* local variable for each dentry as we look at it so that we don't see
* the components of that value change under us */
while (managed = ACCESS_ONCE(path->dentry->d_flags),
managed &= DCACHE_MANAGED_DENTRY,
unlikely(managed != 0)) {
/* Allow the filesystem to manage the transit without i_mutex
* being held. */
if (managed & DCACHE_MANAGE_TRANSIT) {
BUG_ON(!path->dentry->d_op);
BUG_ON(!path->dentry->d_op->d_manage);
ret = path->dentry->d_op->d_manage(path->dentry, false);
if (ret < 0)
break;
}
/* Transit to a mounted filesystem. */
if (managed & DCACHE_MOUNTED) {
struct vfsmount *mounted = lookup_mnt(path);
if (mounted) {
dput(path->dentry);
if (need_mntput)
mntput(path->mnt);
path->mnt = mounted;
path->dentry = dget(mounted->mnt_root);
need_mntput = true;
continue;
}
/* Something is mounted on this dentry in another
* namespace and/or whatever was mounted there in this
* namespace got unmounted before lookup_mnt() could
* get it */
}
/* Handle an automount point */
if (managed & DCACHE_NEED_AUTOMOUNT) {
ret = follow_automount(path, flags, &need_mntput);
if (ret < 0)
break;
continue;
}
/* We didn't change the current path point */
break;
}
if (need_mntput && path->mnt == mnt)
mntput(path->mnt);
if (ret == -EISDIR)
ret = 0;
return ret < 0 ? ret : need_mntput;
}
int follow_down_one(struct path *path)
{
struct vfsmount *mounted;
mounted = lookup_mnt(path);
if (mounted) {
dput(path->dentry);
mntput(path->mnt);
path->mnt = mounted;
path->dentry = dget(mounted->mnt_root);
return 1;
}
return 0;
}
EXPORT_SYMBOL(follow_down_one);
static inline int managed_dentry_rcu(struct dentry *dentry)
{
return (dentry->d_flags & DCACHE_MANAGE_TRANSIT) ?
dentry->d_op->d_manage(dentry, true) : 0;
}
/*
* Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
* we meet a managed dentry that would need blocking.
*/
static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
struct inode **inode)
{
for (;;) {
struct mount *mounted;
/*
* Don't forget we might have a non-mountpoint managed dentry
* that wants to block transit.
*/
switch (managed_dentry_rcu(path->dentry)) {
case -ECHILD:
default:
return false;
case -EISDIR:
return true;
case 0:
break;
}
if (!d_mountpoint(path->dentry))
return !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT);
mounted = __lookup_mnt(path->mnt, path->dentry);
if (!mounted)
break;
path->mnt = &mounted->mnt;
path->dentry = mounted->mnt.mnt_root;
nd->flags |= LOOKUP_JUMPED;
nd->seq = read_seqcount_begin(&path->dentry->d_seq);
/*
* Update the inode too. We don't need to re-check the
* dentry sequence number here after this d_inode read,
* because a mount-point is always pinned.
*/
*inode = path->dentry->d_inode;
}
return !read_seqretry(&mount_lock, nd->m_seq) &&
!(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT);
}
static int follow_dotdot_rcu(struct nameidata *nd)
{
struct inode *inode = nd->inode;
if (!nd->root.mnt)
set_root_rcu(nd);
while (1) {
if (nd->path.dentry == nd->root.dentry &&
nd->path.mnt == nd->root.mnt) {
break;
}
if (nd->path.dentry != nd->path.mnt->mnt_root) {
struct dentry *old = nd->path.dentry;
struct dentry *parent = old->d_parent;
unsigned seq;
inode = parent->d_inode;
seq = read_seqcount_begin(&parent->d_seq);
if (read_seqcount_retry(&old->d_seq, nd->seq))
goto failed;
nd->path.dentry = parent;
nd->seq = seq;
break;
}
if (!follow_up_rcu(&nd->path))
break;
inode = nd->path.dentry->d_inode;
nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
}
while (d_mountpoint(nd->path.dentry)) {
struct mount *mounted;
mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry);
if (!mounted)
break;
nd->path.mnt = &mounted->mnt;
nd->path.dentry = mounted->mnt.mnt_root;
inode = nd->path.dentry->d_inode;
nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
if (read_seqretry(&mount_lock, nd->m_seq))
goto failed;
}
nd->inode = inode;
return 0;
failed:
nd->flags &= ~LOOKUP_RCU;
if (!(nd->flags & LOOKUP_ROOT))
nd->root.mnt = NULL;
rcu_read_unlock();
return -ECHILD;
}
/*
* Follow down to the covering mount currently visible to userspace. At each
* point, the filesystem owning that dentry may be queried as to whether the
* caller is permitted to proceed or not.
*/
int follow_down(struct path *path)
{
unsigned managed;
int ret;
while (managed = ACCESS_ONCE(path->dentry->d_flags),
unlikely(managed & DCACHE_MANAGED_DENTRY)) {
/* Allow the filesystem to manage the transit without i_mutex
* being held.
*
* We indicate to the filesystem if someone is trying to mount
* something here. This gives autofs the chance to deny anyone
* other than its daemon the right to mount on its
* superstructure.
*
* The filesystem may sleep at this point.
*/
if (managed & DCACHE_MANAGE_TRANSIT) {
BUG_ON(!path->dentry->d_op);
BUG_ON(!path->dentry->d_op->d_manage);
ret = path->dentry->d_op->d_manage(
path->dentry, false);
if (ret < 0)
return ret == -EISDIR ? 0 : ret;
}
/* Transit to a mounted filesystem. */
if (managed & DCACHE_MOUNTED) {
struct vfsmount *mounted = lookup_mnt(path);
if (!mounted)
break;
dput(path->dentry);
mntput(path->mnt);
path->mnt = mounted;
path->dentry = dget(mounted->mnt_root);
continue;
}
/* Don't handle automount points here */
break;
}
return 0;
}
EXPORT_SYMBOL(follow_down);
/*
* Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
*/
static void follow_mount(struct path *path)
{
while (d_mountpoint(path->dentry)) {
struct vfsmount *mounted = lookup_mnt(path);
if (!mounted)
break;
dput(path->dentry);
mntput(path->mnt);
path->mnt = mounted;
path->dentry = dget(mounted->mnt_root);
}
}
static void follow_dotdot(struct nameidata *nd)
{
if (!nd->root.mnt)
set_root(nd);
while(1) {
struct dentry *old = nd->path.dentry;
if (nd->path.dentry == nd->root.dentry &&
nd->path.mnt == nd->root.mnt) {
break;
}
if (nd->path.dentry != nd->path.mnt->mnt_root) {
/* rare case of legitimate dget_parent()... */
nd->path.dentry = dget_parent(nd->path.dentry);
dput(old);
break;
}
if (!follow_up(&nd->path))
break;
}
follow_mount(&nd->path);
nd->inode = nd->path.dentry->d_inode;
}
/*
* This looks up the name in dcache, possibly revalidates the old dentry and
* allocates a new one if not found or not valid. In the need_lookup argument
* returns whether i_op->lookup is necessary.
*
* dir->d_inode->i_mutex must be held
*/
static struct dentry *lookup_dcache(struct qstr *name, struct dentry *dir,
unsigned int flags, bool *need_lookup)
{
struct dentry *dentry;
int error;
*need_lookup = false;
dentry = d_lookup(dir, name);
if (dentry) {
if (dentry->d_flags & DCACHE_OP_REVALIDATE) {
error = d_revalidate(dentry, flags);
if (unlikely(error <= 0)) {
if (error < 0) {
dput(dentry);
return ERR_PTR(error);
} else {
d_invalidate(dentry);
dput(dentry);
dentry = NULL;
}
}
}
}
if (!dentry) {
dentry = d_alloc(dir, name);
if (unlikely(!dentry))
return ERR_PTR(-ENOMEM);
*need_lookup = true;
}
return dentry;
}
/*
* Call i_op->lookup on the dentry. The dentry must be negative and
* unhashed.
*
* dir->d_inode->i_mutex must be held
*/
static struct dentry *lookup_real(struct inode *dir, struct dentry *dentry,
unsigned int flags)
{
struct dentry *old;
/* Don't create child dentry for a dead directory. */
if (unlikely(IS_DEADDIR(dir))) {
dput(dentry);
return ERR_PTR(-ENOENT);
}
old = dir->i_op->lookup(dir, dentry, flags);
if (unlikely(old)) {
dput(dentry);
dentry = old;
}
return dentry;
}
static struct dentry *__lookup_hash(struct qstr *name,
struct dentry *base, unsigned int flags)
{
bool need_lookup;
struct dentry *dentry;
dentry = lookup_dcache(name, base, flags, &need_lookup);
if (!need_lookup)
return dentry;
return lookup_real(base->d_inode, dentry, flags);
}
/*
* It's more convoluted than I'd like it to be, but... it's still fairly
* small and for now I'd prefer to have fast path as straight as possible.
* It _is_ time-critical.
*/
static int lookup_fast(struct nameidata *nd,
struct path *path, struct inode **inode)
{
struct vfsmount *mnt = nd->path.mnt;
struct dentry *dentry, *parent = nd->path.dentry;
int need_reval = 1;
int status = 1;
int err;
/*
* Rename seqlock is not required here because in the off chance
* of a false negative due to a concurrent rename, we're going to
* do the non-racy lookup, below.
*/
if (nd->flags & LOOKUP_RCU) {
unsigned seq;
dentry = __d_lookup_rcu(parent, &nd->last, &seq);
if (!dentry)
goto unlazy;
/*
* This sequence count validates that the inode matches
* the dentry name information from lookup.
*/
*inode = dentry->d_inode;
if (read_seqcount_retry(&dentry->d_seq, seq))
return -ECHILD;
/*
* This sequence count validates that the parent had no
* changes while we did the lookup of the dentry above.
*
* The memory barrier in read_seqcount_begin of child is
* enough, we can use __read_seqcount_retry here.
*/
if (__read_seqcount_retry(&parent->d_seq, nd->seq))
return -ECHILD;
nd->seq = seq;
if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) {
status = d_revalidate(dentry, nd->flags);
if (unlikely(status <= 0)) {
if (status != -ECHILD)
need_reval = 0;
goto unlazy;
}
}
path->mnt = mnt;
path->dentry = dentry;
if (likely(__follow_mount_rcu(nd, path, inode)))
return 0;
unlazy:
if (unlazy_walk(nd, dentry))
return -ECHILD;
} else {
dentry = __d_lookup(parent, &nd->last);
}
if (unlikely(!dentry))
goto need_lookup;
if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE) && need_reval)
status = d_revalidate(dentry, nd->flags);
if (unlikely(status <= 0)) {
if (status < 0) {
dput(dentry);
return status;
}
d_invalidate(dentry);
dput(dentry);
goto need_lookup;
}
path->mnt = mnt;
path->dentry = dentry;
err = follow_managed(path, nd->flags);
if (unlikely(err < 0)) {
path_put_conditional(path, nd);
return err;
}
if (err)
nd->flags |= LOOKUP_JUMPED;
*inode = path->dentry->d_inode;
return 0;
need_lookup:
return 1;
}
/* Fast lookup failed, do it the slow way */
static int lookup_slow(struct nameidata *nd, struct path *path)
{
struct dentry *dentry, *parent;
int err;
parent = nd->path.dentry;
BUG_ON(nd->inode != parent->d_inode);
mutex_lock(&parent->d_inode->i_mutex);
dentry = __lookup_hash(&nd->last, parent, nd->flags);
mutex_unlock(&parent->d_inode->i_mutex);
if (IS_ERR(dentry))
return PTR_ERR(dentry);
path->mnt = nd->path.mnt;
path->dentry = dentry;
err = follow_managed(path, nd->flags);
if (unlikely(err < 0)) {
path_put_conditional(path, nd);
return err;
}
if (err)
nd->flags |= LOOKUP_JUMPED;
return 0;
}
static inline int may_lookup(struct nameidata *nd)
{
if (nd->flags & LOOKUP_RCU) {
int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
if (err != -ECHILD)
return err;
if (unlazy_walk(nd, NULL))
return -ECHILD;
}
return inode_permission(nd->inode, MAY_EXEC);
}
static inline int handle_dots(struct nameidata *nd, int type)
{
if (type == LAST_DOTDOT) {
if (nd->flags & LOOKUP_RCU) {
if (follow_dotdot_rcu(nd))
return -ECHILD;
} else
follow_dotdot(nd);
}
return 0;
}
static void terminate_walk(struct nameidata *nd)
{
if (!(nd->flags & LOOKUP_RCU)) {
path_put(&nd->path);
} else {
nd->flags &= ~LOOKUP_RCU;
if (!(nd->flags & LOOKUP_ROOT))
nd->root.mnt = NULL;
rcu_read_unlock();
}
}
/*
* Do we need to follow links? We _really_ want to be able
* to do this check without having to look at inode->i_op,
* so we keep a cache of "no, this doesn't need follow_link"
* for the common case.
*/
static inline int should_follow_link(struct dentry *dentry, int follow)
{
return unlikely(d_is_symlink(dentry)) ? follow : 0;
}
static inline int walk_component(struct nameidata *nd, struct path *path,
int follow)
{
struct inode *inode;
int err;
/*
* "." and ".." are special - ".." especially so because it has
* to be able to know about the current root directory and
* parent relationships.
*/
if (unlikely(nd->last_type != LAST_NORM))
return handle_dots(nd, nd->last_type);
err = lookup_fast(nd, path, &inode);
if (unlikely(err)) {
if (err < 0)
goto out_err;
err = lookup_slow(nd, path);
if (err < 0)
goto out_err;
inode = path->dentry->d_inode;
}
err = -ENOENT;
if (!inode || d_is_negative(path->dentry))
goto out_path_put;
if (should_follow_link(path->dentry, follow)) {
if (nd->flags & LOOKUP_RCU) {
if (unlikely(unlazy_walk(nd, path->dentry))) {
err = -ECHILD;
goto out_err;
}
}
BUG_ON(inode != path->dentry->d_inode);
return 1;
}
path_to_nameidata(path, nd);
nd->inode = inode;
return 0;
out_path_put:
path_to_nameidata(path, nd);
out_err:
terminate_walk(nd);
return err;
}
/*
* This limits recursive symlink follows to 8, while
* limiting consecutive symlinks to 40.
*
* Without that kind of total limit, nasty chains of consecutive
* symlinks can cause almost arbitrarily long lookups.
*/
static inline int nested_symlink(struct path *path, struct nameidata *nd)
{
int res;
if (unlikely(current->link_count >= MAX_NESTED_LINKS)) {
path_put_conditional(path, nd);
path_put(&nd->path);
return -ELOOP;
}
BUG_ON(nd->depth >= MAX_NESTED_LINKS);
nd->depth++;
current->link_count++;
do {
struct path link = *path;
void *cookie;
res = follow_link(&link, nd, &cookie);
if (res)
break;
res = walk_component(nd, path, LOOKUP_FOLLOW);
put_link(nd, &link, cookie);
} while (res > 0);
current->link_count--;
nd->depth--;
return res;
}
/*
* We can do the critical dentry name comparison and hashing
* operations one word at a time, but we are limited to:
*
* - Architectures with fast unaligned word accesses. We could
* do a "get_unaligned()" if this helps and is sufficiently
* fast.
*
* - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
* do not trap on the (extremely unlikely) case of a page
* crossing operation.
*
* - Furthermore, we need an efficient 64-bit compile for the
* 64-bit case in order to generate the "number of bytes in
* the final mask". Again, that could be replaced with a
* efficient population count instruction or similar.
*/
#ifdef CONFIG_DCACHE_WORD_ACCESS
#include <asm/word-at-a-time.h>
#ifdef CONFIG_64BIT
static inline unsigned int fold_hash(unsigned long hash)
{
return hash_64(hash, 32);
}
#else /* 32-bit case */
#define fold_hash(x) (x)
#endif
unsigned int full_name_hash(const unsigned char *name, unsigned int len)
{
unsigned long a, mask;
unsigned long hash = 0;
for (;;) {
a = load_unaligned_zeropad(name);
if (len < sizeof(unsigned long))
break;
hash += a;
hash *= 9;
name += sizeof(unsigned long);
len -= sizeof(unsigned long);
if (!len)
goto done;
}
mask = bytemask_from_count(len);
hash += mask & a;
done:
return fold_hash(hash);
}
EXPORT_SYMBOL(full_name_hash);
/*
* Calculate the length and hash of the path component, and
* return the "hash_len" as the result.
*/
static inline u64 hash_name(const char *name)
{
unsigned long a, b, adata, bdata, mask, hash, len;
const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
hash = a = 0;
len = -sizeof(unsigned long);
do {
hash = (hash + a) * 9;
len += sizeof(unsigned long);
a = load_unaligned_zeropad(name+len);
b = a ^ REPEAT_BYTE('/');
} while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants)));
adata = prep_zero_mask(a, adata, &constants);
bdata = prep_zero_mask(b, bdata, &constants);
mask = create_zero_mask(adata | bdata);
hash += a & zero_bytemask(mask);
len += find_zero(mask);
return hashlen_create(fold_hash(hash), len);
}
#else
unsigned int full_name_hash(const unsigned char *name, unsigned int len)
{
unsigned long hash = init_name_hash();
while (len--)
hash = partial_name_hash(*name++, hash);
return end_name_hash(hash);
}
EXPORT_SYMBOL(full_name_hash);
/*
* We know there's a real path component here of at least
* one character.
*/
static inline u64 hash_name(const char *name)
{
unsigned long hash = init_name_hash();
unsigned long len = 0, c;
c = (unsigned char)*name;
do {
len++;
hash = partial_name_hash(c, hash);
c = (unsigned char)name[len];
} while (c && c != '/');
return hashlen_create(end_name_hash(hash), len);
}
#endif
/*
* Name resolution.
* This is the basic name resolution function, turning a pathname into
* the final dentry. We expect 'base' to be positive and a directory.
*
* Returns 0 and nd will have valid dentry and mnt on success.
* Returns error and drops reference to input namei data on failure.
*/
static int link_path_walk(const char *name, struct nameidata *nd)
{
struct path next;
int err;
while (*name=='/')
name++;
if (!*name)
return 0;
/* At this point we know we have a real path component. */
for(;;) {
u64 hash_len;
int type;
err = may_lookup(nd);
if (err)
break;
hash_len = hash_name(name);
type = LAST_NORM;
if (name[0] == '.') switch (hashlen_len(hash_len)) {
case 2:
if (name[1] == '.') {
type = LAST_DOTDOT;
nd->flags |= LOOKUP_JUMPED;
}
break;
case 1:
type = LAST_DOT;
}
if (likely(type == LAST_NORM)) {
struct dentry *parent = nd->path.dentry;
nd->flags &= ~LOOKUP_JUMPED;
if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
struct qstr this = { { .hash_len = hash_len }, .name = name };
err = parent->d_op->d_hash(parent, &this);
if (err < 0)
break;
hash_len = this.hash_len;
name = this.name;
}
}
nd->last.hash_len = hash_len;
nd->last.name = name;
nd->last_type = type;
name += hashlen_len(hash_len);
if (!*name)
return 0;
/*
* If it wasn't NUL, we know it was '/'. Skip that
* slash, and continue until no more slashes.
*/
do {
name++;
} while (unlikely(*name == '/'));
if (!*name)
return 0;
err = walk_component(nd, &next, LOOKUP_FOLLOW);
if (err < 0)
return err;
if (err) {
err = nested_symlink(&next, nd);
if (err)
return err;
}
if (!d_can_lookup(nd->path.dentry)) {
err = -ENOTDIR;
break;
}
}
terminate_walk(nd);
return err;
}
static int path_init(int dfd, const struct filename *name, unsigned int flags,
struct nameidata *nd)
{
int retval = 0;
const char *s = name->name;
nd->last_type = LAST_ROOT; /* if there are only slashes... */
nd->flags = flags | LOOKUP_JUMPED | LOOKUP_PARENT;
nd->depth = 0;
nd->base = NULL;
if (flags & LOOKUP_ROOT) {
struct dentry *root = nd->root.dentry;
struct inode *inode = root->d_inode;
if (*s) {
if (!d_can_lookup(root))
return -ENOTDIR;
retval = inode_permission(inode, MAY_EXEC);
if (retval)
return retval;
}
nd->path = nd->root;
nd->inode = inode;
if (flags & LOOKUP_RCU) {
rcu_read_lock();
nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
nd->m_seq = read_seqbegin(&mount_lock);
} else {
path_get(&nd->path);
}
goto done;
}
nd->root.mnt = NULL;
nd->m_seq = read_seqbegin(&mount_lock);
if (*s == '/') {
if (flags & LOOKUP_RCU) {
rcu_read_lock();
nd->seq = set_root_rcu(nd);
} else {
set_root(nd);
path_get(&nd->root);
}
nd->path = nd->root;
} else if (dfd == AT_FDCWD) {
if (flags & LOOKUP_RCU) {
struct fs_struct *fs = current->fs;
unsigned seq;
rcu_read_lock();
do {
seq = read_seqcount_begin(&fs->seq);
nd->path = fs->pwd;
nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
} while (read_seqcount_retry(&fs->seq, seq));
} else {
get_fs_pwd(current->fs, &nd->path);
}
} else {
/* Caller must check execute permissions on the starting path component */
struct fd f = fdget_raw(dfd);
struct dentry *dentry;
if (!f.file)
return -EBADF;
dentry = f.file->f_path.dentry;
if (*s) {
if (!d_can_lookup(dentry)) {
fdput(f);
return -ENOTDIR;
}
}
nd->path = f.file->f_path;
if (flags & LOOKUP_RCU) {
if (f.flags & FDPUT_FPUT)
nd->base = f.file;
nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
rcu_read_lock();
} else {
path_get(&nd->path);
fdput(f);
}
}
nd->inode = nd->path.dentry->d_inode;
if (!(flags & LOOKUP_RCU))
goto done;
if (likely(!read_seqcount_retry(&nd->path.dentry->d_seq, nd->seq)))
goto done;
if (!(nd->flags & LOOKUP_ROOT))
nd->root.mnt = NULL;
rcu_read_unlock();
return -ECHILD;
done:
current->total_link_count = 0;
return link_path_walk(s, nd);
}
static void path_cleanup(struct nameidata *nd)
{
if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
path_put(&nd->root);
nd->root.mnt = NULL;
}
if (unlikely(nd->base))
fput(nd->base);
}
static inline int lookup_last(struct nameidata *nd, struct path *path)
{
if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len])
nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
nd->flags &= ~LOOKUP_PARENT;
return walk_component(nd, path, nd->flags & LOOKUP_FOLLOW);
}
/* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
static int path_lookupat(int dfd, const struct filename *name,
unsigned int flags, struct nameidata *nd)
{
struct path path;
int err;
/*
* Path walking is largely split up into 2 different synchronisation
* schemes, rcu-walk and ref-walk (explained in
* Documentation/filesystems/path-lookup.txt). These share much of the
* path walk code, but some things particularly setup, cleanup, and
* following mounts are sufficiently divergent that functions are
* duplicated. Typically there is a function foo(), and its RCU
* analogue, foo_rcu().
*
* -ECHILD is the error number of choice (just to avoid clashes) that
* is returned if some aspect of an rcu-walk fails. Such an error must
* be handled by restarting a traditional ref-walk (which will always
* be able to complete).
*/
err = path_init(dfd, name, flags, nd);
if (!err && !(flags & LOOKUP_PARENT)) {
err = lookup_last(nd, &path);
while (err > 0) {
void *cookie;
struct path link = path;
err = may_follow_link(&link, nd);
if (unlikely(err))
break;
nd->flags |= LOOKUP_PARENT;
err = follow_link(&link, nd, &cookie);
if (err)
break;
err = lookup_last(nd, &path);
put_link(nd, &link, cookie);
}
}
if (!err)
err = complete_walk(nd);
if (!err && nd->flags & LOOKUP_DIRECTORY) {
if (!d_can_lookup(nd->path.dentry)) {
path_put(&nd->path);
err = -ENOTDIR;
}
}
path_cleanup(nd);
return err;
}
static int filename_lookup(int dfd, struct filename *name,
unsigned int flags, struct nameidata *nd)
{
int retval = path_lookupat(dfd, name, flags | LOOKUP_RCU, nd);
if (unlikely(retval == -ECHILD))
retval = path_lookupat(dfd, name, flags, nd);
if (unlikely(retval == -ESTALE))
retval = path_lookupat(dfd, name, flags | LOOKUP_REVAL, nd);
if (likely(!retval))
audit_inode(name, nd->path.dentry, flags & LOOKUP_PARENT);
return retval;
}
/* does lookup, returns the object with parent locked */
struct dentry *kern_path_locked(const char *name, struct path *path)
{
struct filename *filename = getname_kernel(name);
struct nameidata nd;
struct dentry *d;
int err;
if (IS_ERR(filename))
return ERR_CAST(filename);
err = filename_lookup(AT_FDCWD, filename, LOOKUP_PARENT, &nd);
if (err) {
d = ERR_PTR(err);
goto out;
}
if (nd.last_type != LAST_NORM) {
path_put(&nd.path);
d = ERR_PTR(-EINVAL);
goto out;
}
mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
d = __lookup_hash(&nd.last, nd.path.dentry, 0);
if (IS_ERR(d)) {
mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
path_put(&nd.path);
goto out;
}
*path = nd.path;
out:
putname(filename);
return d;
}
int kern_path(const char *name, unsigned int flags, struct path *path)
{
struct nameidata nd;
struct filename *filename = getname_kernel(name);
int res = PTR_ERR(filename);
if (!IS_ERR(filename)) {
res = filename_lookup(AT_FDCWD, filename, flags, &nd);
putname(filename);
if (!res)
*path = nd.path;
}
return res;
}
EXPORT_SYMBOL(kern_path);
/**
* vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
* @dentry: pointer to dentry of the base directory
* @mnt: pointer to vfs mount of the base directory
* @name: pointer to file name
* @flags: lookup flags
* @path: pointer to struct path to fill
*/
int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
const char *name, unsigned int flags,
struct path *path)
{
struct filename *filename = getname_kernel(name);
int err = PTR_ERR(filename);
BUG_ON(flags & LOOKUP_PARENT);
/* the first argument of filename_lookup() is ignored with LOOKUP_ROOT */
if (!IS_ERR(filename)) {
struct nameidata nd;
nd.root.dentry = dentry;
nd.root.mnt = mnt;
err = filename_lookup(AT_FDCWD, filename,
flags | LOOKUP_ROOT, &nd);
if (!err)
*path = nd.path;
putname(filename);
}
return err;
}
EXPORT_SYMBOL(vfs_path_lookup);
/*
* Restricted form of lookup. Doesn't follow links, single-component only,
* needs parent already locked. Doesn't follow mounts.
* SMP-safe.
*/
static struct dentry *lookup_hash(struct nameidata *nd)
{
return __lookup_hash(&nd->last, nd->path.dentry, nd->flags);
}
/**
* lookup_one_len - filesystem helper to lookup single pathname component
* @name: pathname component to lookup
* @base: base directory to lookup from
* @len: maximum length @len should be interpreted to
*
* Note that this routine is purely a helper for filesystem usage and should
* not be called by generic code.
*/
struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
{
struct qstr this;
unsigned int c;
int err;
WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex));
this.name = name;
this.len = len;
this.hash = full_name_hash(name, len);
if (!len)
return ERR_PTR(-EACCES);
if (unlikely(name[0] == '.')) {
if (len < 2 || (len == 2 && name[1] == '.'))
return ERR_PTR(-EACCES);
}
while (len--) {
c = *(const unsigned char *)name++;
if (c == '/' || c == '\0')
return ERR_PTR(-EACCES);
}
/*
* See if the low-level filesystem might want
* to use its own hash..
*/
if (base->d_flags & DCACHE_OP_HASH) {
int err = base->d_op->d_hash(base, &this);
if (err < 0)
return ERR_PTR(err);
}
err = inode_permission(base->d_inode, MAY_EXEC);
if (err)
return ERR_PTR(err);
return __lookup_hash(&this, base, 0);
}
EXPORT_SYMBOL(lookup_one_len);
int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
struct path *path, int *empty)
{
struct nameidata nd;
struct filename *tmp = getname_flags(name, flags, empty);
int err = PTR_ERR(tmp);
if (!IS_ERR(tmp)) {
BUG_ON(flags & LOOKUP_PARENT);
err = filename_lookup(dfd, tmp, flags, &nd);
putname(tmp);
if (!err)
*path = nd.path;
}
return err;
}
int user_path_at(int dfd, const char __user *name, unsigned flags,
struct path *path)
{
return user_path_at_empty(dfd, name, flags, path, NULL);
}
EXPORT_SYMBOL(user_path_at);
/*
* NB: most callers don't do anything directly with the reference to the
* to struct filename, but the nd->last pointer points into the name string
* allocated by getname. So we must hold the reference to it until all
* path-walking is complete.
*/
static struct filename *
user_path_parent(int dfd, const char __user *path, struct nameidata *nd,
unsigned int flags)
{
struct filename *s = getname(path);
int error;
/* only LOOKUP_REVAL is allowed in extra flags */
flags &= LOOKUP_REVAL;
if (IS_ERR(s))
return s;
error = filename_lookup(dfd, s, flags | LOOKUP_PARENT, nd);
if (error) {
putname(s);
return ERR_PTR(error);
}
return s;
}
/**
* mountpoint_last - look up last component for umount
* @nd: pathwalk nameidata - currently pointing at parent directory of "last"
* @path: pointer to container for result
*
* This is a special lookup_last function just for umount. In this case, we
* need to resolve the path without doing any revalidation.
*
* The nameidata should be the result of doing a LOOKUP_PARENT pathwalk. Since
* mountpoints are always pinned in the dcache, their ancestors are too. Thus,
* in almost all cases, this lookup will be served out of the dcache. The only
* cases where it won't are if nd->last refers to a symlink or the path is
* bogus and it doesn't exist.
*
* Returns:
* -error: if there was an error during lookup. This includes -ENOENT if the
* lookup found a negative dentry. The nd->path reference will also be
* put in this case.
*
* 0: if we successfully resolved nd->path and found it to not to be a
* symlink that needs to be followed. "path" will also be populated.
* The nd->path reference will also be put.
*
* 1: if we successfully resolved nd->last and found it to be a symlink
* that needs to be followed. "path" will be populated with the path
* to the link, and nd->path will *not* be put.
*/
static int
mountpoint_last(struct nameidata *nd, struct path *path)
{
int error = 0;
struct dentry *dentry;
struct dentry *dir = nd->path.dentry;
/* If we're in rcuwalk, drop out of it to handle last component */
if (nd->flags & LOOKUP_RCU) {
if (unlazy_walk(nd, NULL)) {
error = -ECHILD;
goto out;
}
}
nd->flags &= ~LOOKUP_PARENT;
if (unlikely(nd->last_type != LAST_NORM)) {
error = handle_dots(nd, nd->last_type);
if (error)
goto out;
dentry = dget(nd->path.dentry);
goto done;
}
mutex_lock(&dir->d_inode->i_mutex);
dentry = d_lookup(dir, &nd->last);
if (!dentry) {
/*
* No cached dentry. Mounted dentries are pinned in the cache,
* so that means that this dentry is probably a symlink or the
* path doesn't actually point to a mounted dentry.
*/
dentry = d_alloc(dir, &nd->last);
if (!dentry) {
error = -ENOMEM;
mutex_unlock(&dir->d_inode->i_mutex);
goto out;
}
dentry = lookup_real(dir->d_inode, dentry, nd->flags);
error = PTR_ERR(dentry);
if (IS_ERR(dentry)) {
mutex_unlock(&dir->d_inode->i_mutex);
goto out;
}
}
mutex_unlock(&dir->d_inode->i_mutex);
done:
if (!dentry->d_inode || d_is_negative(dentry)) {
error = -ENOENT;
dput(dentry);
goto out;
}
path->dentry = dentry;
path->mnt = nd->path.mnt;
if (should_follow_link(dentry, nd->flags & LOOKUP_FOLLOW))
return 1;
mntget(path->mnt);
follow_mount(path);
error = 0;
out:
terminate_walk(nd);
return error;
}
/**
* path_mountpoint - look up a path to be umounted
* @dfd: directory file descriptor to start walk from
* @name: full pathname to walk
* @path: pointer to container for result
* @flags: lookup flags
*
* Look up the given name, but don't attempt to revalidate the last component.
* Returns 0 and "path" will be valid on success; Returns error otherwise.
*/
static int
path_mountpoint(int dfd, const struct filename *name, struct path *path,
unsigned int flags)
{
struct nameidata nd;
int err;
err = path_init(dfd, name, flags, &nd);
if (unlikely(err))
goto out;
err = mountpoint_last(&nd, path);
while (err > 0) {
void *cookie;
struct path link = *path;
err = may_follow_link(&link, &nd);
if (unlikely(err))
break;
nd.flags |= LOOKUP_PARENT;
err = follow_link(&link, &nd, &cookie);
if (err)
break;
err = mountpoint_last(&nd, path);
put_link(&nd, &link, cookie);
}
out:
path_cleanup(&nd);
return err;
}
static int
filename_mountpoint(int dfd, struct filename *name, struct path *path,
unsigned int flags)
{
int error;
if (IS_ERR(name))
return PTR_ERR(name);
error = path_mountpoint(dfd, name, path, flags | LOOKUP_RCU);
if (unlikely(error == -ECHILD))
error = path_mountpoint(dfd, name, path, flags);
if (unlikely(error == -ESTALE))
error = path_mountpoint(dfd, name, path, flags | LOOKUP_REVAL);
if (likely(!error))
audit_inode(name, path->dentry, 0);
putname(name);
return error;
}
/**
* user_path_mountpoint_at - lookup a path from userland in order to umount it
* @dfd: directory file descriptor
* @name: pathname from userland
* @flags: lookup flags
* @path: pointer to container to hold result
*
* A umount is a special case for path walking. We're not actually interested
* in the inode in this situation, and ESTALE errors can be a problem. We
* simply want track down the dentry and vfsmount attached at the mountpoint
* and avoid revalidating the last component.
*
* Returns 0 and populates "path" on success.
*/
int
user_path_mountpoint_at(int dfd, const char __user *name, unsigned int flags,
struct path *path)
{
return filename_mountpoint(dfd, getname(name), path, flags);
}
int
kern_path_mountpoint(int dfd, const char *name, struct path *path,
unsigned int flags)
{
return filename_mountpoint(dfd, getname_kernel(name), path, flags);
}
EXPORT_SYMBOL(kern_path_mountpoint);
int __check_sticky(struct inode *dir, struct inode *inode)
{
kuid_t fsuid = current_fsuid();
if (uid_eq(inode->i_uid, fsuid))
return 0;
if (uid_eq(dir->i_uid, fsuid))
return 0;
return !capable_wrt_inode_uidgid(inode, CAP_FOWNER);
}
EXPORT_SYMBOL(__check_sticky);
/*
* Check whether we can remove a link victim from directory dir, check
* whether the type of victim is right.
* 1. We can't do it if dir is read-only (done in permission())
* 2. We should have write and exec permissions on dir
* 3. We can't remove anything from append-only dir
* 4. We can't do anything with immutable dir (done in permission())
* 5. If the sticky bit on dir is set we should either
* a. be owner of dir, or
* b. be owner of victim, or
* c. have CAP_FOWNER capability
* 6. If the victim is append-only or immutable we can't do antyhing with
* links pointing to it.
* 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
* 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
* 9. We can't remove a root or mountpoint.
* 10. We don't allow removal of NFS sillyrenamed files; it's handled by
* nfs_async_unlink().
*/
static int may_delete(struct inode *dir, struct dentry *victim, bool isdir)
{
struct inode *inode = victim->d_inode;
int error;
if (d_is_negative(victim))
return -ENOENT;
BUG_ON(!inode);
BUG_ON(victim->d_parent->d_inode != dir);
audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE);
error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
if (error)
return error;
if (IS_APPEND(dir))
return -EPERM;
if (check_sticky(dir, inode) || IS_APPEND(inode) ||
IS_IMMUTABLE(inode) || IS_SWAPFILE(inode))
return -EPERM;
if (isdir) {
if (!d_is_dir(victim))
return -ENOTDIR;
if (IS_ROOT(victim))
return -EBUSY;
} else if (d_is_dir(victim))
return -EISDIR;
if (IS_DEADDIR(dir))
return -ENOENT;
if (victim->d_flags & DCACHE_NFSFS_RENAMED)
return -EBUSY;
return 0;
}
/* Check whether we can create an object with dentry child in directory
* dir.
* 1. We can't do it if child already exists (open has special treatment for
* this case, but since we are inlined it's OK)
* 2. We can't do it if dir is read-only (done in permission())
* 3. We should have write and exec permissions on dir
* 4. We can't do it if dir is immutable (done in permission())
*/
static inline int may_create(struct inode *dir, struct dentry *child)
{
audit_inode_child(dir, child, AUDIT_TYPE_CHILD_CREATE);
if (child->d_inode)
return -EEXIST;
if (IS_DEADDIR(dir))
return -ENOENT;
return inode_permission(dir, MAY_WRITE | MAY_EXEC);
}
/*
* p1 and p2 should be directories on the same fs.
*/
struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
{
struct dentry *p;
if (p1 == p2) {
mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
return NULL;
}
mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
p = d_ancestor(p2, p1);
if (p) {
mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT);
mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD);
return p;
}
p = d_ancestor(p1, p2);
if (p) {
mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
return p;
}
mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT2);
return NULL;
}
EXPORT_SYMBOL(lock_rename);
void unlock_rename(struct dentry *p1, struct dentry *p2)
{
mutex_unlock(&p1->d_inode->i_mutex);
if (p1 != p2) {
mutex_unlock(&p2->d_inode->i_mutex);
mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
}
}
EXPORT_SYMBOL(unlock_rename);
int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
bool want_excl)
{
int error = may_create(dir, dentry);
if (error)
return error;
if (!dir->i_op->create)
return -EACCES; /* shouldn't it be ENOSYS? */
mode &= S_IALLUGO;
mode |= S_IFREG;
error = security_inode_create(dir, dentry, mode);
if (error)
return error;
error = dir->i_op->create(dir, dentry, mode, want_excl);
if (!error)
fsnotify_create(dir, dentry);
return error;
}
EXPORT_SYMBOL(vfs_create);
static int may_open(struct path *path, int acc_mode, int flag)
{
struct dentry *dentry = path->dentry;
struct inode *inode = dentry->d_inode;
int error;
/* O_PATH? */
if (!acc_mode)
return 0;
if (!inode)
return -ENOENT;
switch (inode->i_mode & S_IFMT) {
case S_IFLNK:
return -ELOOP;
case S_IFDIR:
if (acc_mode & MAY_WRITE)
return -EISDIR;
break;
case S_IFBLK:
case S_IFCHR:
if (path->mnt->mnt_flags & MNT_NODEV)
return -EACCES;
/*FALLTHRU*/
case S_IFIFO:
case S_IFSOCK:
flag &= ~O_TRUNC;
break;
}
error = inode_permission(inode, acc_mode);
if (error)
return error;
/*
* An append-only file must be opened in append mode for writing.
*/
if (IS_APPEND(inode)) {
if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
return -EPERM;
if (flag & O_TRUNC)
return -EPERM;
}
/* O_NOATIME can only be set by the owner or superuser */
if (flag & O_NOATIME && !inode_owner_or_capable(inode))
return -EPERM;
return 0;
}
static int handle_truncate(struct file *filp)
{
struct path *path = &filp->f_path;
struct inode *inode = path->dentry->d_inode;
int error = get_write_access(inode);
if (error)
return error;
/*
* Refuse to truncate files with mandatory locks held on them.
*/
error = locks_verify_locked(filp);
if (!error)
error = security_path_truncate(path);
if (!error) {
error = do_truncate(path->dentry, 0,
ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
filp);
}
put_write_access(inode);
return error;
}
static inline int open_to_namei_flags(int flag)
{
if ((flag & O_ACCMODE) == 3)
flag--;
return flag;
}
static int may_o_create(struct path *dir, struct dentry *dentry, umode_t mode)
{
int error = security_path_mknod(dir, dentry, mode, 0);
if (error)
return error;
error = inode_permission(dir->dentry->d_inode, MAY_WRITE | MAY_EXEC);
if (error)
return error;
return security_inode_create(dir->dentry->d_inode, dentry, mode);
}
/*
* Attempt to atomically look up, create and open a file from a negative
* dentry.
*
* Returns 0 if successful. The file will have been created and attached to
* @file by the filesystem calling finish_open().
*
* Returns 1 if the file was looked up only or didn't need creating. The
* caller will need to perform the open themselves. @path will have been
* updated to point to the new dentry. This may be negative.
*
* Returns an error code otherwise.
*/
static int atomic_open(struct nameidata *nd, struct dentry *dentry,
struct path *path, struct file *file,
const struct open_flags *op,
bool got_write, bool need_lookup,
int *opened)
{
struct inode *dir = nd->path.dentry->d_inode;
unsigned open_flag = open_to_namei_flags(op->open_flag);
umode_t mode;
int error;
int acc_mode;
int create_error = 0;
struct dentry *const DENTRY_NOT_SET = (void *) -1UL;
bool excl;
BUG_ON(dentry->d_inode);
/* Don't create child dentry for a dead directory. */
if (unlikely(IS_DEADDIR(dir))) {
error = -ENOENT;
goto out;
}
mode = op->mode;
if ((open_flag & O_CREAT) && !IS_POSIXACL(dir))
mode &= ~current_umask();
excl = (open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT);
if (excl)
open_flag &= ~O_TRUNC;
/*
* Checking write permission is tricky, bacuse we don't know if we are
* going to actually need it: O_CREAT opens should work as long as the
* file exists. But checking existence breaks atomicity. The trick is
* to check access and if not granted clear O_CREAT from the flags.
*
* Another problem is returing the "right" error value (e.g. for an
* O_EXCL open we want to return EEXIST not EROFS).
*/
if (((open_flag & (O_CREAT | O_TRUNC)) ||
(open_flag & O_ACCMODE) != O_RDONLY) && unlikely(!got_write)) {
if (!(open_flag & O_CREAT)) {
/*
* No O_CREATE -> atomicity not a requirement -> fall
* back to lookup + open
*/
goto no_open;
} else if (open_flag & (O_EXCL | O_TRUNC)) {
/* Fall back and fail with the right error */
create_error = -EROFS;
goto no_open;
} else {
/* No side effects, safe to clear O_CREAT */
create_error = -EROFS;
open_flag &= ~O_CREAT;
}
}
if (open_flag & O_CREAT) {
error = may_o_create(&nd->path, dentry, mode);
if (error) {
create_error = error;
if (open_flag & O_EXCL)
goto no_open;
open_flag &= ~O_CREAT;
}
}
if (nd->flags & LOOKUP_DIRECTORY)
open_flag |= O_DIRECTORY;
file->f_path.dentry = DENTRY_NOT_SET;
file->f_path.mnt = nd->path.mnt;
error = dir->i_op->atomic_open(dir, dentry, file, open_flag, mode,
opened);
if (error < 0) {
if (create_error && error == -ENOENT)
error = create_error;
goto out;
}
if (error) { /* returned 1, that is */
if (WARN_ON(file->f_path.dentry == DENTRY_NOT_SET)) {
error = -EIO;
goto out;
}
if (file->f_path.dentry) {
dput(dentry);
dentry = file->f_path.dentry;
}
if (*opened & FILE_CREATED)
fsnotify_create(dir, dentry);
if (!dentry->d_inode) {
WARN_ON(*opened & FILE_CREATED);
if (create_error) {
error = create_error;
goto out;
}
} else {
if (excl && !(*opened & FILE_CREATED)) {
error = -EEXIST;
goto out;
}
}
goto looked_up;
}
/*
* We didn't have the inode before the open, so check open permission
* here.
*/
acc_mode = op->acc_mode;
if (*opened & FILE_CREATED) {
WARN_ON(!(open_flag & O_CREAT));
fsnotify_create(dir, dentry);
acc_mode = MAY_OPEN;
}
error = may_open(&file->f_path, acc_mode, open_flag);
if (error)
fput(file);
out:
dput(dentry);
return error;
no_open:
if (need_lookup) {
dentry = lookup_real(dir, dentry, nd->flags);
if (IS_ERR(dentry))
return PTR_ERR(dentry);
if (create_error) {
int open_flag = op->open_flag;
error = create_error;
if ((open_flag & O_EXCL)) {
if (!dentry->d_inode)
goto out;
} else if (!dentry->d_inode) {
goto out;
} else if ((open_flag & O_TRUNC) &&
d_is_reg(dentry)) {
goto out;
}
/* will fail later, go on to get the right error */
}
}
looked_up:
path->dentry = dentry;
path->mnt = nd->path.mnt;
return 1;
}
/*
* Look up and maybe create and open the last component.
*
* Must be called with i_mutex held on parent.
*
* Returns 0 if the file was successfully atomically created (if necessary) and
* opened. In this case the file will be returned attached to @file.
*
* Returns 1 if the file was not completely opened at this time, though lookups
* and creations will have been performed and the dentry returned in @path will
* be positive upon return if O_CREAT was specified. If O_CREAT wasn't
* specified then a negative dentry may be returned.
*
* An error code is returned otherwise.
*
* FILE_CREATE will be set in @*opened if the dentry was created and will be
* cleared otherwise prior to returning.
*/
static int lookup_open(struct nameidata *nd, struct path *path,
struct file *file,
const struct open_flags *op,
bool got_write, int *opened)
{
struct dentry *dir = nd->path.dentry;
struct inode *dir_inode = dir->d_inode;
struct dentry *dentry;
int error;
bool need_lookup;
*opened &= ~FILE_CREATED;
dentry = lookup_dcache(&nd->last, dir, nd->flags, &need_lookup);
if (IS_ERR(dentry))
return PTR_ERR(dentry);
/* Cached positive dentry: will open in f_op->open */
if (!need_lookup && dentry->d_inode)
goto out_no_open;
if ((nd->flags & LOOKUP_OPEN) && dir_inode->i_op->atomic_open) {
return atomic_open(nd, dentry, path, file, op, got_write,
need_lookup, opened);
}
if (need_lookup) {
BUG_ON(dentry->d_inode);
dentry = lookup_real(dir_inode, dentry, nd->flags);
if (IS_ERR(dentry))
return PTR_ERR(dentry);
}
/* Negative dentry, just create the file */
if (!dentry->d_inode && (op->open_flag & O_CREAT)) {
umode_t mode = op->mode;
if (!IS_POSIXACL(dir->d_inode))
mode &= ~current_umask();
/*
* This write is needed to ensure that a
* rw->ro transition does not occur between
* the time when the file is created and when
* a permanent write count is taken through
* the 'struct file' in finish_open().
*/
if (!got_write) {
error = -EROFS;
goto out_dput;
}
*opened |= FILE_CREATED;
error = security_path_mknod(&nd->path, dentry, mode, 0);
if (error)
goto out_dput;
error = vfs_create(dir->d_inode, dentry, mode,
nd->flags & LOOKUP_EXCL);
if (error)
goto out_dput;
}
out_no_open:
path->dentry = dentry;
path->mnt = nd->path.mnt;
return 1;
out_dput:
dput(dentry);
return error;
}
/*
* Handle the last step of open()
*/
static int do_last(struct nameidata *nd, struct path *path,
struct file *file, const struct open_flags *op,
int *opened, struct filename *name)
{
struct dentry *dir = nd->path.dentry;
int open_flag = op->open_flag;
bool will_truncate = (open_flag & O_TRUNC) != 0;
bool got_write = false;
int acc_mode = op->acc_mode;
struct inode *inode;
bool symlink_ok = false;
struct path save_parent = { .dentry = NULL, .mnt = NULL };
bool retried = false;
int error;
nd->flags &= ~LOOKUP_PARENT;
nd->flags |= op->intent;
if (nd->last_type != LAST_NORM) {
error = handle_dots(nd, nd->last_type);
if (error)
return error;
goto finish_open;
}
if (!(open_flag & O_CREAT)) {
if (nd->last.name[nd->last.len])
nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW))
symlink_ok = true;
/* we _can_ be in RCU mode here */
error = lookup_fast(nd, path, &inode);
if (likely(!error))
goto finish_lookup;
if (error < 0)
goto out;
BUG_ON(nd->inode != dir->d_inode);
} else {
/* create side of things */
/*
* This will *only* deal with leaving RCU mode - LOOKUP_JUMPED
* has been cleared when we got to the last component we are
* about to look up
*/
error = complete_walk(nd);
if (error)
return error;
audit_inode(name, dir, LOOKUP_PARENT);
error = -EISDIR;
/* trailing slashes? */
if (nd->last.name[nd->last.len])
goto out;
}
retry_lookup:
if (op->open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
error = mnt_want_write(nd->path.mnt);
if (!error)
got_write = true;
/*
* do _not_ fail yet - we might not need that or fail with
* a different error; let lookup_open() decide; we'll be
* dropping this one anyway.
*/
}
mutex_lock(&dir->d_inode->i_mutex);
error = lookup_open(nd, path, file, op, got_write, opened);
mutex_unlock(&dir->d_inode->i_mutex);
if (error <= 0) {
if (error)
goto out;
if ((*opened & FILE_CREATED) ||
!S_ISREG(file_inode(file)->i_mode))
will_truncate = false;
audit_inode(name, file->f_path.dentry, 0);
goto opened;
}
if (*opened & FILE_CREATED) {
/* Don't check for write permission, don't truncate */
open_flag &= ~O_TRUNC;
will_truncate = false;
acc_mode = MAY_OPEN;
path_to_nameidata(path, nd);
goto finish_open_created;
}
/*
* create/update audit record if it already exists.
*/
if (d_is_positive(path->dentry))
audit_inode(name, path->dentry, 0);
/*
* If atomic_open() acquired write access it is dropped now due to
* possible mount and symlink following (this might be optimized away if
* necessary...)
*/
if (got_write) {
mnt_drop_write(nd->path.mnt);
got_write = false;
}
error = -EEXIST;
if ((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT))
goto exit_dput;
error = follow_managed(path, nd->flags);
if (error < 0)
goto exit_dput;
if (error)
nd->flags |= LOOKUP_JUMPED;
BUG_ON(nd->flags & LOOKUP_RCU);
inode = path->dentry->d_inode;
finish_lookup:
/* we _can_ be in RCU mode here */
error = -ENOENT;
if (!inode || d_is_negative(path->dentry)) {
path_to_nameidata(path, nd);
goto out;
}
if (should_follow_link(path->dentry, !symlink_ok)) {
if (nd->flags & LOOKUP_RCU) {
if (unlikely(unlazy_walk(nd, path->dentry))) {
error = -ECHILD;
goto out;
}
}
BUG_ON(inode != path->dentry->d_inode);
return 1;
}
if ((nd->flags & LOOKUP_RCU) || nd->path.mnt != path->mnt) {
path_to_nameidata(path, nd);
} else {
save_parent.dentry = nd->path.dentry;
save_parent.mnt = mntget(path->mnt);
nd->path.dentry = path->dentry;
}
nd->inode = inode;
/* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
finish_open:
error = complete_walk(nd);
if (error) {
path_put(&save_parent);
return error;
}
audit_inode(name, nd->path.dentry, 0);
error = -EISDIR;
if ((open_flag & O_CREAT) && d_is_dir(nd->path.dentry))
goto out;
error = -ENOTDIR;
if ((nd->flags & LOOKUP_DIRECTORY) && !d_can_lookup(nd->path.dentry))
goto out;
if (!S_ISREG(nd->inode->i_mode))
will_truncate = false;
if (will_truncate) {
error = mnt_want_write(nd->path.mnt);
if (error)
goto out;
got_write = true;
}
finish_open_created:
error = may_open(&nd->path, acc_mode, open_flag);
if (error)
goto out;
BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */
error = vfs_open(&nd->path, file, current_cred());
if (!error) {
*opened |= FILE_OPENED;
} else {
if (error == -EOPENSTALE)
goto stale_open;
goto out;
}
opened:
error = open_check_o_direct(file);
if (error)
goto exit_fput;
error = ima_file_check(file, op->acc_mode, *opened);
if (error)
goto exit_fput;
if (will_truncate) {
error = handle_truncate(file);
if (error)
goto exit_fput;
}
out:
if (got_write)
mnt_drop_write(nd->path.mnt);
path_put(&save_parent);
terminate_walk(nd);
return error;
exit_dput:
path_put_conditional(path, nd);
goto out;
exit_fput:
fput(file);
goto out;
stale_open:
/* If no saved parent or already retried then can't retry */
if (!save_parent.dentry || retried)
goto out;
BUG_ON(save_parent.dentry != dir);
path_put(&nd->path);
nd->path = save_parent;
nd->inode = dir->d_inode;
save_parent.mnt = NULL;
save_parent.dentry = NULL;
if (got_write) {
mnt_drop_write(nd->path.mnt);
got_write = false;
}
retried = true;
goto retry_lookup;
}
static int do_tmpfile(int dfd, struct filename *pathname,
struct nameidata *nd, int flags,
const struct open_flags *op,
struct file *file, int *opened)
{
static const struct qstr name = QSTR_INIT("/", 1);
struct dentry *dentry, *child;
struct inode *dir;
int error = path_lookupat(dfd, pathname,
flags | LOOKUP_DIRECTORY, nd);
if (unlikely(error))
return error;
error = mnt_want_write(nd->path.mnt);
if (unlikely(error))
goto out;
/* we want directory to be writable */
error = inode_permission(nd->inode, MAY_WRITE | MAY_EXEC);
if (error)
goto out2;
dentry = nd->path.dentry;
dir = dentry->d_inode;
if (!dir->i_op->tmpfile) {
error = -EOPNOTSUPP;
goto out2;
}
child = d_alloc(dentry, &name);
if (unlikely(!child)) {
error = -ENOMEM;
goto out2;
}
nd->flags &= ~LOOKUP_DIRECTORY;
nd->flags |= op->intent;
dput(nd->path.dentry);
nd->path.dentry = child;
error = dir->i_op->tmpfile(dir, nd->path.dentry, op->mode);
if (error)
goto out2;
audit_inode(pathname, nd->path.dentry, 0);
/* Don't check for other permissions, the inode was just created */
error = may_open(&nd->path, MAY_OPEN, op->open_flag);
if (error)
goto out2;
file->f_path.mnt = nd->path.mnt;
error = finish_open(file, nd->path.dentry, NULL, opened);
if (error)
goto out2;
error = open_check_o_direct(file);
if (error) {
fput(file);
} else if (!(op->open_flag & O_EXCL)) {
struct inode *inode = file_inode(file);
spin_lock(&inode->i_lock);
inode->i_state |= I_LINKABLE;
spin_unlock(&inode->i_lock);
}
out2:
mnt_drop_write(nd->path.mnt);
out:
path_put(&nd->path);
return error;
}
static struct file *path_openat(int dfd, struct filename *pathname,
struct nameidata *nd, const struct open_flags *op, int flags)
{
struct file *file;
struct path path;
int opened = 0;
int error;
file = get_empty_filp();
if (IS_ERR(file))
return file;
file->f_flags = op->open_flag;
if (unlikely(file->f_flags & __O_TMPFILE)) {
error = do_tmpfile(dfd, pathname, nd, flags, op, file, &opened);
goto out;
}
error = path_init(dfd, pathname, flags, nd);
if (unlikely(error))
goto out;
error = do_last(nd, &path, file, op, &opened, pathname);
while (unlikely(error > 0)) { /* trailing symlink */
struct path link = path;
void *cookie;
if (!(nd->flags & LOOKUP_FOLLOW)) {
path_put_conditional(&path, nd);
path_put(&nd->path);
error = -ELOOP;
break;
}
error = may_follow_link(&link, nd);
if (unlikely(error))
break;
nd->flags |= LOOKUP_PARENT;
nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
error = follow_link(&link, nd, &cookie);
if (unlikely(error))
break;
error = do_last(nd, &path, file, op, &opened, pathname);
put_link(nd, &link, cookie);
}
out:
path_cleanup(nd);
if (!(opened & FILE_OPENED)) {
BUG_ON(!error);
put_filp(file);
}
if (unlikely(error)) {
if (error == -EOPENSTALE) {
if (flags & LOOKUP_RCU)
error = -ECHILD;
else
error = -ESTALE;
}
file = ERR_PTR(error);
}
return file;
}
struct file *do_filp_open(int dfd, struct filename *pathname,
const struct open_flags *op)
{
struct nameidata nd;
int flags = op->lookup_flags;
struct file *filp;
filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_RCU);
if (unlikely(filp == ERR_PTR(-ECHILD)))
filp = path_openat(dfd, pathname, &nd, op, flags);
if (unlikely(filp == ERR_PTR(-ESTALE)))
filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_REVAL);
return filp;
}
struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
const char *name, const struct open_flags *op)
{
struct nameidata nd;
struct file *file;
struct filename *filename;
int flags = op->lookup_flags | LOOKUP_ROOT;
nd.root.mnt = mnt;
nd.root.dentry = dentry;
if (d_is_symlink(dentry) && op->intent & LOOKUP_OPEN)
return ERR_PTR(-ELOOP);
filename = getname_kernel(name);
if (unlikely(IS_ERR(filename)))
return ERR_CAST(filename);
file = path_openat(-1, filename, &nd, op, flags | LOOKUP_RCU);
if (unlikely(file == ERR_PTR(-ECHILD)))
file = path_openat(-1, filename, &nd, op, flags);
if (unlikely(file == ERR_PTR(-ESTALE)))
file = path_openat(-1, filename, &nd, op, flags | LOOKUP_REVAL);
putname(filename);
return file;
}
static struct dentry *filename_create(int dfd, struct filename *name,
struct path *path, unsigned int lookup_flags)
{
struct dentry *dentry = ERR_PTR(-EEXIST);
struct nameidata nd;
int err2;
int error;
bool is_dir = (lookup_flags & LOOKUP_DIRECTORY);
/*
* Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any
* other flags passed in are ignored!
*/
lookup_flags &= LOOKUP_REVAL;
error = filename_lookup(dfd, name, LOOKUP_PARENT|lookup_flags, &nd);
if (error)
return ERR_PTR(error);
/*
* Yucky last component or no last component at all?
* (foo/., foo/.., /////)
*/
if (nd.last_type != LAST_NORM)
goto out;
nd.flags &= ~LOOKUP_PARENT;
nd.flags |= LOOKUP_CREATE | LOOKUP_EXCL;
/* don't fail immediately if it's r/o, at least try to report other errors */
err2 = mnt_want_write(nd.path.mnt);
/*
* Do the final lookup.
*/
mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
dentry = lookup_hash(&nd);
if (IS_ERR(dentry))
goto unlock;
error = -EEXIST;
if (d_is_positive(dentry))
goto fail;
/*
* Special case - lookup gave negative, but... we had foo/bar/
* From the vfs_mknod() POV we just have a negative dentry -
* all is fine. Let's be bastards - you had / on the end, you've
* been asking for (non-existent) directory. -ENOENT for you.
*/
if (unlikely(!is_dir && nd.last.name[nd.last.len])) {
error = -ENOENT;
goto fail;
}
if (unlikely(err2)) {
error = err2;
goto fail;
}
*path = nd.path;
return dentry;
fail:
dput(dentry);
dentry = ERR_PTR(error);
unlock:
mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
if (!err2)
mnt_drop_write(nd.path.mnt);
out:
path_put(&nd.path);
return dentry;
}
struct dentry *kern_path_create(int dfd, const char *pathname,
struct path *path, unsigned int lookup_flags)
{
struct filename *filename = getname_kernel(pathname);
struct dentry *res;
if (IS_ERR(filename))
return ERR_CAST(filename);
res = filename_create(dfd, filename, path, lookup_flags);
putname(filename);
return res;
}
EXPORT_SYMBOL(kern_path_create);
void done_path_create(struct path *path, struct dentry *dentry)
{
dput(dentry);
mutex_unlock(&path->dentry->d_inode->i_mutex);
mnt_drop_write(path->mnt);
path_put(path);
}
EXPORT_SYMBOL(done_path_create);
struct dentry *user_path_create(int dfd, const char __user *pathname,
struct path *path, unsigned int lookup_flags)
{
struct filename *tmp = getname(pathname);
struct dentry *res;
if (IS_ERR(tmp))
return ERR_CAST(tmp);
res = filename_create(dfd, tmp, path, lookup_flags);
putname(tmp);
return res;
}
EXPORT_SYMBOL(user_path_create);
int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
{
int error = may_create(dir, dentry);
if (error)
return error;
if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
return -EPERM;
if (!dir->i_op->mknod)
return -EPERM;
error = devcgroup_inode_mknod(mode, dev);
if (error)
return error;
error = security_inode_mknod(dir, dentry, mode, dev);
if (error)
return error;
error = dir->i_op->mknod(dir, dentry, mode, dev);
if (!error)
fsnotify_create(dir, dentry);
return error;
}
EXPORT_SYMBOL(vfs_mknod);
static int may_mknod(umode_t mode)
{
switch (mode & S_IFMT) {
case S_IFREG:
case S_IFCHR:
case S_IFBLK:
case S_IFIFO:
case S_IFSOCK:
case 0: /* zero mode translates to S_IFREG */
return 0;
case S_IFDIR:
return -EPERM;
default:
return -EINVAL;
}
}
SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode,
unsigned, dev)
{
struct dentry *dentry;
struct path path;
int error;
unsigned int lookup_flags = 0;
error = may_mknod(mode);
if (error)
return error;
retry:
dentry = user_path_create(dfd, filename, &path, lookup_flags);
if (IS_ERR(dentry))
return PTR_ERR(dentry);
if (!IS_POSIXACL(path.dentry->d_inode))
mode &= ~current_umask();
error = security_path_mknod(&path, dentry, mode, dev);
if (error)
goto out;
switch (mode & S_IFMT) {
case 0: case S_IFREG:
error = vfs_create(path.dentry->d_inode,dentry,mode,true);
break;
case S_IFCHR: case S_IFBLK:
error = vfs_mknod(path.dentry->d_inode,dentry,mode,
new_decode_dev(dev));
break;
case S_IFIFO: case S_IFSOCK:
error = vfs_mknod(path.dentry->d_inode,dentry,mode,0);
break;
}
out:
done_path_create(&path, dentry);
if (retry_estale(error, lookup_flags)) {
lookup_flags |= LOOKUP_REVAL;
goto retry;
}
return error;
}
SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev)
{
return sys_mknodat(AT_FDCWD, filename, mode, dev);
}
int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
{
int error = may_create(dir, dentry);
unsigned max_links = dir->i_sb->s_max_links;
if (error)
return error;
if (!dir->i_op->mkdir)
return -EPERM;
mode &= (S_IRWXUGO|S_ISVTX);
error = security_inode_mkdir(dir, dentry, mode);
if (error)
return error;
if (max_links && dir->i_nlink >= max_links)
return -EMLINK;
error = dir->i_op->mkdir(dir, dentry, mode);
if (!error)
fsnotify_mkdir(dir, dentry);
return error;
}
EXPORT_SYMBOL(vfs_mkdir);
SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode)
{
struct dentry *dentry;
struct path path;
int error;
unsigned int lookup_flags = LOOKUP_DIRECTORY;
retry:
dentry = user_path_create(dfd, pathname, &path, lookup_flags);
if (IS_ERR(dentry))
return PTR_ERR(dentry);
if (!IS_POSIXACL(path.dentry->d_inode))
mode &= ~current_umask();
error = security_path_mkdir(&path, dentry, mode);
if (!error)
error = vfs_mkdir(path.dentry->d_inode, dentry, mode);
done_path_create(&path, dentry);
if (retry_estale(error, lookup_flags)) {
lookup_flags |= LOOKUP_REVAL;
goto retry;
}
return error;
}
SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode)
{
return sys_mkdirat(AT_FDCWD, pathname, mode);
}
/*
* The dentry_unhash() helper will try to drop the dentry early: we
* should have a usage count of 1 if we're the only user of this
* dentry, and if that is true (possibly after pruning the dcache),
* then we drop the dentry now.
*
* A low-level filesystem can, if it choses, legally
* do a
*
* if (!d_unhashed(dentry))
* return -EBUSY;
*
* if it cannot handle the case of removing a directory
* that is still in use by something else..
*/
void dentry_unhash(struct dentry *dentry)
{
shrink_dcache_parent(dentry);
spin_lock(&dentry->d_lock);
if (dentry->d_lockref.count == 1)
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
}
EXPORT_SYMBOL(dentry_unhash);
int vfs_rmdir(struct inode *dir, struct dentry *dentry)
{
int error = may_delete(dir, dentry, 1);
if (error)
return error;
if (!dir->i_op->rmdir)
return -EPERM;
dget(dentry);
mutex_lock(&dentry->d_inode->i_mutex);
error = -EBUSY;
if (is_local_mountpoint(dentry))
goto out;
error = security_inode_rmdir(dir, dentry);
if (error)
goto out;
shrink_dcache_parent(dentry);
error = dir->i_op->rmdir(dir, dentry);
if (error)
goto out;
dentry->d_inode->i_flags |= S_DEAD;
dont_mount(dentry);
detach_mounts(dentry);
out:
mutex_unlock(&dentry->d_inode->i_mutex);
dput(dentry);
if (!error)
d_delete(dentry);
return error;
}
EXPORT_SYMBOL(vfs_rmdir);
static long do_rmdir(int dfd, const char __user *pathname)
{
int error = 0;
struct filename *name;
struct dentry *dentry;
struct nameidata nd;
unsigned int lookup_flags = 0;
retry:
name = user_path_parent(dfd, pathname, &nd, lookup_flags);
if (IS_ERR(name))
return PTR_ERR(name);
switch(nd.last_type) {
case LAST_DOTDOT:
error = -ENOTEMPTY;
goto exit1;
case LAST_DOT:
error = -EINVAL;
goto exit1;
case LAST_ROOT:
error = -EBUSY;
goto exit1;
}
nd.flags &= ~LOOKUP_PARENT;
error = mnt_want_write(nd.path.mnt);
if (error)
goto exit1;
mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
dentry = lookup_hash(&nd);
error = PTR_ERR(dentry);
if (IS_ERR(dentry))
goto exit2;
if (!dentry->d_inode) {
error = -ENOENT;
goto exit3;
}
error = security_path_rmdir(&nd.path, dentry);
if (error)
goto exit3;
error = vfs_rmdir(nd.path.dentry->d_inode, dentry);
exit3:
dput(dentry);
exit2:
mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
mnt_drop_write(nd.path.mnt);
exit1:
path_put(&nd.path);
putname(name);
if (retry_estale(error, lookup_flags)) {
lookup_flags |= LOOKUP_REVAL;
goto retry;
}
return error;
}
SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
{
return do_rmdir(AT_FDCWD, pathname);
}
/**
* vfs_unlink - unlink a filesystem object
* @dir: parent directory
* @dentry: victim
* @delegated_inode: returns victim inode, if the inode is delegated.
*
* The caller must hold dir->i_mutex.
*
* If vfs_unlink discovers a delegation, it will return -EWOULDBLOCK and
* return a reference to the inode in delegated_inode. The caller
* should then break the delegation on that inode and retry. Because
* breaking a delegation may take a long time, the caller should drop
* dir->i_mutex before doing so.
*
* Alternatively, a caller may pass NULL for delegated_inode. This may
* be appropriate for callers that expect the underlying filesystem not
* to be NFS exported.
*/
int vfs_unlink(struct inode *dir, struct dentry *dentry, struct inode **delegated_inode)
{
struct inode *target = dentry->d_inode;
int error = may_delete(dir, dentry, 0);
if (error)
return error;
if (!dir->i_op->unlink)
return -EPERM;
mutex_lock(&target->i_mutex);
if (is_local_mountpoint(dentry))
error = -EBUSY;
else {
error = security_inode_unlink(dir, dentry);
if (!error) {
error = try_break_deleg(target, delegated_inode);
if (error)
goto out;
error = dir->i_op->unlink(dir, dentry);
if (!error) {
dont_mount(dentry);
detach_mounts(dentry);
}
}
}
out:
mutex_unlock(&target->i_mutex);
/* We don't d_delete() NFS sillyrenamed files--they still exist. */
if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
fsnotify_link_count(target);
d_delete(dentry);
}
return error;
}
EXPORT_SYMBOL(vfs_unlink);
/*
* Make sure that the actual truncation of the file will occur outside its
* directory's i_mutex. Truncate can take a long time if there is a lot of
* writeout happening, and we don't want to prevent access to the directory
* while waiting on the I/O.
*/
static long do_unlinkat(int dfd, const char __user *pathname)
{
int error;
struct filename *name;
struct dentry *dentry;
struct nameidata nd;
struct inode *inode = NULL;
struct inode *delegated_inode = NULL;
unsigned int lookup_flags = 0;
retry:
name = user_path_parent(dfd, pathname, &nd, lookup_flags);
if (IS_ERR(name))
return PTR_ERR(name);
error = -EISDIR;
if (nd.last_type != LAST_NORM)
goto exit1;
nd.flags &= ~LOOKUP_PARENT;
error = mnt_want_write(nd.path.mnt);
if (error)
goto exit1;
retry_deleg:
mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
dentry = lookup_hash(&nd);
error = PTR_ERR(dentry);
if (!IS_ERR(dentry)) {
/* Why not before? Because we want correct error value */
if (nd.last.name[nd.last.len])
goto slashes;
inode = dentry->d_inode;
if (d_is_negative(dentry))
goto slashes;
ihold(inode);
error = security_path_unlink(&nd.path, dentry);
if (error)
goto exit2;
error = vfs_unlink(nd.path.dentry->d_inode, dentry, &delegated_inode);
exit2:
dput(dentry);
}
mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
if (inode)
iput(inode); /* truncate the inode here */
inode = NULL;
if (delegated_inode) {
error = break_deleg_wait(&delegated_inode);
if (!error)
goto retry_deleg;
}
mnt_drop_write(nd.path.mnt);
exit1:
path_put(&nd.path);
putname(name);
if (retry_estale(error, lookup_flags)) {
lookup_flags |= LOOKUP_REVAL;
inode = NULL;
goto retry;
}
return error;
slashes:
if (d_is_negative(dentry))
error = -ENOENT;
else if (d_is_dir(dentry))
error = -EISDIR;
else
error = -ENOTDIR;
goto exit2;
}
SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
{
if ((flag & ~AT_REMOVEDIR) != 0)
return -EINVAL;
if (flag & AT_REMOVEDIR)
return do_rmdir(dfd, pathname);
return do_unlinkat(dfd, pathname);
}
SYSCALL_DEFINE1(unlink, const char __user *, pathname)
{
return do_unlinkat(AT_FDCWD, pathname);
}
int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname)
{
int error = may_create(dir, dentry);
if (error)
return error;
if (!dir->i_op->symlink)
return -EPERM;
error = security_inode_symlink(dir, dentry, oldname);
if (error)
return error;
error = dir->i_op->symlink(dir, dentry, oldname);
if (!error)
fsnotify_create(dir, dentry);
return error;
}
EXPORT_SYMBOL(vfs_symlink);
SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
int, newdfd, const char __user *, newname)
{
int error;
struct filename *from;
struct dentry *dentry;
struct path path;
unsigned int lookup_flags = 0;
from = getname(oldname);
if (IS_ERR(from))
return PTR_ERR(from);
retry:
dentry = user_path_create(newdfd, newname, &path, lookup_flags);
error = PTR_ERR(dentry);
if (IS_ERR(dentry))
goto out_putname;
error = security_path_symlink(&path, dentry, from->name);
if (!error)
error = vfs_symlink(path.dentry->d_inode, dentry, from->name);
done_path_create(&path, dentry);
if (retry_estale(error, lookup_flags)) {
lookup_flags |= LOOKUP_REVAL;
goto retry;
}
out_putname:
putname(from);
return error;
}
SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
{
return sys_symlinkat(oldname, AT_FDCWD, newname);
}
/**
* vfs_link - create a new link
* @old_dentry: object to be linked
* @dir: new parent
* @new_dentry: where to create the new link
* @delegated_inode: returns inode needing a delegation break
*
* The caller must hold dir->i_mutex
*
* If vfs_link discovers a delegation on the to-be-linked file in need
* of breaking, it will return -EWOULDBLOCK and return a reference to the
* inode in delegated_inode. The caller should then break the delegation
* and retry. Because breaking a delegation may take a long time, the
* caller should drop the i_mutex before doing so.
*
* Alternatively, a caller may pass NULL for delegated_inode. This may
* be appropriate for callers that expect the underlying filesystem not
* to be NFS exported.
*/
int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry, struct inode **delegated_inode)
{
struct inode *inode = old_dentry->d_inode;
unsigned max_links = dir->i_sb->s_max_links;
int error;
if (!inode)
return -ENOENT;
error = may_create(dir, new_dentry);
if (error)
return error;
if (dir->i_sb != inode->i_sb)
return -EXDEV;
/*
* A link to an append-only or immutable file cannot be created.
*/
if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
return -EPERM;
if (!dir->i_op->link)
return -EPERM;
if (S_ISDIR(inode->i_mode))
return -EPERM;
error = security_inode_link(old_dentry, dir, new_dentry);
if (error)
return error;
mutex_lock(&inode->i_mutex);
/* Make sure we don't allow creating hardlink to an unlinked file */
if (inode->i_nlink == 0 && !(inode->i_state & I_LINKABLE))
error = -ENOENT;
else if (max_links && inode->i_nlink >= max_links)
error = -EMLINK;
else {
error = try_break_deleg(inode, delegated_inode);
if (!error)
error = dir->i_op->link(old_dentry, dir, new_dentry);
}
if (!error && (inode->i_state & I_LINKABLE)) {
spin_lock(&inode->i_lock);
inode->i_state &= ~I_LINKABLE;
spin_unlock(&inode->i_lock);
}
mutex_unlock(&inode->i_mutex);
if (!error)
fsnotify_link(dir, inode, new_dentry);
return error;
}
EXPORT_SYMBOL(vfs_link);
/*
* Hardlinks are often used in delicate situations. We avoid
* security-related surprises by not following symlinks on the
* newname. --KAB
*
* We don't follow them on the oldname either to be compatible
* with linux 2.0, and to avoid hard-linking to directories
* and other special files. --ADM
*/
SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
int, newdfd, const char __user *, newname, int, flags)
{
struct dentry *new_dentry;
struct path old_path, new_path;
struct inode *delegated_inode = NULL;
int how = 0;
int error;
if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
return -EINVAL;
/*
* To use null names we require CAP_DAC_READ_SEARCH
* This ensures that not everyone will be able to create
* handlink using the passed filedescriptor.
*/
if (flags & AT_EMPTY_PATH) {
if (!capable(CAP_DAC_READ_SEARCH))
return -ENOENT;
how = LOOKUP_EMPTY;
}
if (flags & AT_SYMLINK_FOLLOW)
how |= LOOKUP_FOLLOW;
retry:
error = user_path_at(olddfd, oldname, how, &old_path);
if (error)
return error;
new_dentry = user_path_create(newdfd, newname, &new_path,
(how & LOOKUP_REVAL));
error = PTR_ERR(new_dentry);
if (IS_ERR(new_dentry))
goto out;
error = -EXDEV;
if (old_path.mnt != new_path.mnt)
goto out_dput;
error = may_linkat(&old_path);
if (unlikely(error))
goto out_dput;
error = security_path_link(old_path.dentry, &new_path, new_dentry);
if (error)
goto out_dput;
error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry, &delegated_inode);
out_dput:
done_path_create(&new_path, new_dentry);
if (delegated_inode) {
error = break_deleg_wait(&delegated_inode);
if (!error) {
path_put(&old_path);
goto retry;
}
}
if (retry_estale(error, how)) {
path_put(&old_path);
how |= LOOKUP_REVAL;
goto retry;
}
out:
path_put(&old_path);
return error;
}
SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
{
return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
}
/**
* vfs_rename - rename a filesystem object
* @old_dir: parent of source
* @old_dentry: source
* @new_dir: parent of destination
* @new_dentry: destination
* @delegated_inode: returns an inode needing a delegation break
* @flags: rename flags
*
* The caller must hold multiple mutexes--see lock_rename()).
*
* If vfs_rename discovers a delegation in need of breaking at either
* the source or destination, it will return -EWOULDBLOCK and return a
* reference to the inode in delegated_inode. The caller should then
* break the delegation and retry. Because breaking a delegation may
* take a long time, the caller should drop all locks before doing
* so.
*
* Alternatively, a caller may pass NULL for delegated_inode. This may
* be appropriate for callers that expect the underlying filesystem not
* to be NFS exported.
*
* The worst of all namespace operations - renaming directory. "Perverted"
* doesn't even start to describe it. Somebody in UCB had a heck of a trip...
* Problems:
* a) we can get into loop creation.
* b) race potential - two innocent renames can create a loop together.
* That's where 4.4 screws up. Current fix: serialization on
* sb->s_vfs_rename_mutex. We might be more accurate, but that's another
* story.
* c) we have to lock _four_ objects - parents and victim (if it exists),
* and source (if it is not a directory).
* And that - after we got ->i_mutex on parents (until then we don't know
* whether the target exists). Solution: try to be smart with locking
* order for inodes. We rely on the fact that tree topology may change
* only under ->s_vfs_rename_mutex _and_ that parent of the object we
* move will be locked. Thus we can rank directories by the tree
* (ancestors first) and rank all non-directories after them.
* That works since everybody except rename does "lock parent, lookup,
* lock child" and rename is under ->s_vfs_rename_mutex.
* HOWEVER, it relies on the assumption that any object with ->lookup()
* has no more than 1 dentry. If "hybrid" objects will ever appear,
* we'd better make sure that there's no link(2) for them.
* d) conversion from fhandle to dentry may come in the wrong moment - when
* we are removing the target. Solution: we will have to grab ->i_mutex
* in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
* ->i_mutex on parents, which works but leads to some truly excessive
* locking].
*/
int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
struct inode *new_dir, struct dentry *new_dentry,
struct inode **delegated_inode, unsigned int flags)
{
int error;
bool is_dir = d_is_dir(old_dentry);
const unsigned char *old_name;
struct inode *source = old_dentry->d_inode;
struct inode *target = new_dentry->d_inode;
bool new_is_dir = false;
unsigned max_links = new_dir->i_sb->s_max_links;
if (source == target)
return 0;
error = may_delete(old_dir, old_dentry, is_dir);
if (error)
return error;
if (!target) {
error = may_create(new_dir, new_dentry);
} else {
new_is_dir = d_is_dir(new_dentry);
if (!(flags & RENAME_EXCHANGE))
error = may_delete(new_dir, new_dentry, is_dir);
else
error = may_delete(new_dir, new_dentry, new_is_dir);
}
if (error)
return error;
if (!old_dir->i_op->rename && !old_dir->i_op->rename2)
return -EPERM;
if (flags && !old_dir->i_op->rename2)
return -EINVAL;
/*
* If we are going to change the parent - check write permissions,
* we'll need to flip '..'.
*/
if (new_dir != old_dir) {
if (is_dir) {
error = inode_permission(source, MAY_WRITE);
if (error)
return error;
}
if ((flags & RENAME_EXCHANGE) && new_is_dir) {
error = inode_permission(target, MAY_WRITE);
if (error)
return error;
}
}
error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry,
flags);
if (error)
return error;
old_name = fsnotify_oldname_init(old_dentry->d_name.name);
dget(new_dentry);
if (!is_dir || (flags & RENAME_EXCHANGE))
lock_two_nondirectories(source, target);
else if (target)
mutex_lock(&target->i_mutex);
error = -EBUSY;
if (is_local_mountpoint(old_dentry) || is_local_mountpoint(new_dentry))
goto out;
if (max_links && new_dir != old_dir) {
error = -EMLINK;
if (is_dir && !new_is_dir && new_dir->i_nlink >= max_links)
goto out;
if ((flags & RENAME_EXCHANGE) && !is_dir && new_is_dir &&
old_dir->i_nlink >= max_links)
goto out;
}
if (is_dir && !(flags & RENAME_EXCHANGE) && target)
shrink_dcache_parent(new_dentry);
if (!is_dir) {
error = try_break_deleg(source, delegated_inode);
if (error)
goto out;
}
if (target && !new_is_dir) {
error = try_break_deleg(target, delegated_inode);
if (error)
goto out;
}
if (!old_dir->i_op->rename2) {
error = old_dir->i_op->rename(old_dir, old_dentry,
new_dir, new_dentry);
} else {
WARN_ON(old_dir->i_op->rename != NULL);
error = old_dir->i_op->rename2(old_dir, old_dentry,
new_dir, new_dentry, flags);
}
if (error)
goto out;
if (!(flags & RENAME_EXCHANGE) && target) {
if (is_dir)
target->i_flags |= S_DEAD;
dont_mount(new_dentry);
detach_mounts(new_dentry);
}
if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) {
if (!(flags & RENAME_EXCHANGE))
d_move(old_dentry, new_dentry);
else
d_exchange(old_dentry, new_dentry);
}
out:
if (!is_dir || (flags & RENAME_EXCHANGE))
unlock_two_nondirectories(source, target);
else if (target)
mutex_unlock(&target->i_mutex);
dput(new_dentry);
if (!error) {
fsnotify_move(old_dir, new_dir, old_name, is_dir,
!(flags & RENAME_EXCHANGE) ? target : NULL, old_dentry);
if (flags & RENAME_EXCHANGE) {
fsnotify_move(new_dir, old_dir, old_dentry->d_name.name,
new_is_dir, NULL, new_dentry);
}
}
fsnotify_oldname_free(old_name);
return error;
}
EXPORT_SYMBOL(vfs_rename);
SYSCALL_DEFINE5(renameat2, int, olddfd, const char __user *, oldname,
int, newdfd, const char __user *, newname, unsigned int, flags)
{
struct dentry *old_dir, *new_dir;
struct dentry *old_dentry, *new_dentry;
struct dentry *trap;
struct nameidata oldnd, newnd;
struct inode *delegated_inode = NULL;
struct filename *from;
struct filename *to;
unsigned int lookup_flags = 0;
bool should_retry = false;
int error;
if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
return -EINVAL;
if ((flags & (RENAME_NOREPLACE | RENAME_WHITEOUT)) &&
(flags & RENAME_EXCHANGE))
return -EINVAL;
if ((flags & RENAME_WHITEOUT) && !capable(CAP_MKNOD))
return -EPERM;
retry:
from = user_path_parent(olddfd, oldname, &oldnd, lookup_flags);
if (IS_ERR(from)) {
error = PTR_ERR(from);
goto exit;
}
to = user_path_parent(newdfd, newname, &newnd, lookup_flags);
if (IS_ERR(to)) {
error = PTR_ERR(to);
goto exit1;
}
error = -EXDEV;
if (oldnd.path.mnt != newnd.path.mnt)
goto exit2;
old_dir = oldnd.path.dentry;
error = -EBUSY;
if (oldnd.last_type != LAST_NORM)
goto exit2;
new_dir = newnd.path.dentry;
if (flags & RENAME_NOREPLACE)
error = -EEXIST;
if (newnd.last_type != LAST_NORM)
goto exit2;
error = mnt_want_write(oldnd.path.mnt);
if (error)
goto exit2;
oldnd.flags &= ~LOOKUP_PARENT;
newnd.flags &= ~LOOKUP_PARENT;
if (!(flags & RENAME_EXCHANGE))
newnd.flags |= LOOKUP_RENAME_TARGET;
retry_deleg:
trap = lock_rename(new_dir, old_dir);
old_dentry = lookup_hash(&oldnd);
error = PTR_ERR(old_dentry);
if (IS_ERR(old_dentry))
goto exit3;
/* source must exist */
error = -ENOENT;
if (d_is_negative(old_dentry))
goto exit4;
new_dentry = lookup_hash(&newnd);
error = PTR_ERR(new_dentry);
if (IS_ERR(new_dentry))
goto exit4;
error = -EEXIST;
if ((flags & RENAME_NOREPLACE) && d_is_positive(new_dentry))
goto exit5;
if (flags & RENAME_EXCHANGE) {
error = -ENOENT;
if (d_is_negative(new_dentry))
goto exit5;
if (!d_is_dir(new_dentry)) {
error = -ENOTDIR;
if (newnd.last.name[newnd.last.len])
goto exit5;
}
}
/* unless the source is a directory trailing slashes give -ENOTDIR */
if (!d_is_dir(old_dentry)) {
error = -ENOTDIR;
if (oldnd.last.name[oldnd.last.len])
goto exit5;
if (!(flags & RENAME_EXCHANGE) && newnd.last.name[newnd.last.len])
goto exit5;
}
/* source should not be ancestor of target */
error = -EINVAL;
if (old_dentry == trap)
goto exit5;
/* target should not be an ancestor of source */
if (!(flags & RENAME_EXCHANGE))
error = -ENOTEMPTY;
if (new_dentry == trap)
goto exit5;
error = security_path_rename(&oldnd.path, old_dentry,
&newnd.path, new_dentry, flags);
if (error)
goto exit5;
error = vfs_rename(old_dir->d_inode, old_dentry,
new_dir->d_inode, new_dentry,
&delegated_inode, flags);
exit5:
dput(new_dentry);
exit4:
dput(old_dentry);
exit3:
unlock_rename(new_dir, old_dir);
if (delegated_inode) {
error = break_deleg_wait(&delegated_inode);
if (!error)
goto retry_deleg;
}
mnt_drop_write(oldnd.path.mnt);
exit2:
if (retry_estale(error, lookup_flags))
should_retry = true;
path_put(&newnd.path);
putname(to);
exit1:
path_put(&oldnd.path);
putname(from);
if (should_retry) {
should_retry = false;
lookup_flags |= LOOKUP_REVAL;
goto retry;
}
exit:
return error;
}
SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
int, newdfd, const char __user *, newname)
{
return sys_renameat2(olddfd, oldname, newdfd, newname, 0);
}
SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
{
return sys_renameat2(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
}
int vfs_whiteout(struct inode *dir, struct dentry *dentry)
{
int error = may_create(dir, dentry);
if (error)
return error;
if (!dir->i_op->mknod)
return -EPERM;
return dir->i_op->mknod(dir, dentry,
S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV);
}
EXPORT_SYMBOL(vfs_whiteout);
int readlink_copy(char __user *buffer, int buflen, const char *link)
{
int len = PTR_ERR(link);
if (IS_ERR(link))
goto out;
len = strlen(link);
if (len > (unsigned) buflen)
len = buflen;
if (copy_to_user(buffer, link, len))
len = -EFAULT;
out:
return len;
}
EXPORT_SYMBOL(readlink_copy);
/*
* A helper for ->readlink(). This should be used *ONLY* for symlinks that
* have ->follow_link() touching nd only in nd_set_link(). Using (or not
* using) it for any given inode is up to filesystem.
*/
int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
{
struct nameidata nd;
void *cookie;
int res;
nd.depth = 0;
cookie = dentry->d_inode->i_op->follow_link(dentry, &nd);
if (IS_ERR(cookie))
return PTR_ERR(cookie);
res = readlink_copy(buffer, buflen, nd_get_link(&nd));
if (dentry->d_inode->i_op->put_link)
dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
return res;
}
EXPORT_SYMBOL(generic_readlink);
/* get the link contents into pagecache */
static char *page_getlink(struct dentry * dentry, struct page **ppage)
{
char *kaddr;
struct page *page;
struct address_space *mapping = dentry->d_inode->i_mapping;
page = read_mapping_page(mapping, 0, NULL);
if (IS_ERR(page))
return (char*)page;
*ppage = page;
kaddr = kmap(page);
nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1);
return kaddr;
}
int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
{
struct page *page = NULL;
int res = readlink_copy(buffer, buflen, page_getlink(dentry, &page));
if (page) {
kunmap(page);
page_cache_release(page);
}
return res;
}
EXPORT_SYMBOL(page_readlink);
void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
{
struct page *page = NULL;
nd_set_link(nd, page_getlink(dentry, &page));
return page;
}
EXPORT_SYMBOL(page_follow_link_light);
void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
{
struct page *page = cookie;
if (page) {
kunmap(page);
page_cache_release(page);
}
}
EXPORT_SYMBOL(page_put_link);
/*
* The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
*/
int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
{
struct address_space *mapping = inode->i_mapping;
struct page *page;
void *fsdata;
int err;
char *kaddr;
unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE;
if (nofs)
flags |= AOP_FLAG_NOFS;
retry:
err = pagecache_write_begin(NULL, mapping, 0, len-1,
flags, &page, &fsdata);
if (err)
goto fail;
kaddr = kmap_atomic(page);
memcpy(kaddr, symname, len-1);
kunmap_atomic(kaddr);
err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
page, fsdata);
if (err < 0)
goto fail;
if (err < len-1)
goto retry;
mark_inode_dirty(inode);
return 0;
fail:
return err;
}
EXPORT_SYMBOL(__page_symlink);
int page_symlink(struct inode *inode, const char *symname, int len)
{
return __page_symlink(inode, symname, len,
!(mapping_gfp_mask(inode->i_mapping) & __GFP_FS));
}
EXPORT_SYMBOL(page_symlink);
const struct inode_operations page_symlink_inode_operations = {
.readlink = generic_readlink,
.follow_link = page_follow_link_light,
.put_link = page_put_link,
};
EXPORT_SYMBOL(page_symlink_inode_operations);
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