kernel_optimize_test/fs/overlayfs/inode.c
Vivek Goyal 500cac3cce ovl: append MAY_READ when diluting write checks
Right now we remove MAY_WRITE/MAY_APPEND bits from mask if realfile is on
lower/. This is done as files on lower will never be written and will be
copied up. But to copy up a file, mounter should have MAY_READ permission
otherwise copy up will fail. So set MAY_READ in mask when MAY_WRITE is
reset.

Dan Walsh noticed this when he did access(lowerfile, W_OK) and it returned
True (context mounts) but when he tried to actually write to file, it
failed as mounter did not have permission on lower file.

[SzM] don't set MAY_READ if only MAY_APPEND is set without MAY_WRITE; this
won't trigger a copy-up.

Reported-by: Dan Walsh <dwalsh@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-07-29 12:05:24 +02:00

481 lines
10 KiB
C

/*
*
* Copyright (C) 2011 Novell Inc.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 as published by
* the Free Software Foundation.
*/
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/xattr.h>
#include "overlayfs.h"
static int ovl_copy_up_truncate(struct dentry *dentry)
{
int err;
struct dentry *parent;
struct kstat stat;
struct path lowerpath;
parent = dget_parent(dentry);
err = ovl_copy_up(parent);
if (err)
goto out_dput_parent;
ovl_path_lower(dentry, &lowerpath);
err = vfs_getattr(&lowerpath, &stat);
if (err)
goto out_dput_parent;
stat.size = 0;
err = ovl_copy_up_one(parent, dentry, &lowerpath, &stat);
out_dput_parent:
dput(parent);
return err;
}
int ovl_setattr(struct dentry *dentry, struct iattr *attr)
{
int err;
struct dentry *upperdentry;
const struct cred *old_cred;
/*
* Check for permissions before trying to copy-up. This is redundant
* since it will be rechecked later by ->setattr() on upper dentry. But
* without this, copy-up can be triggered by just about anybody.
*
* We don't initialize inode->size, which just means that
* inode_newsize_ok() will always check against MAX_LFS_FILESIZE and not
* check for a swapfile (which this won't be anyway).
*/
err = inode_change_ok(dentry->d_inode, attr);
if (err)
return err;
err = ovl_want_write(dentry);
if (err)
goto out;
if (attr->ia_valid & ATTR_SIZE) {
struct inode *realinode = d_inode(ovl_dentry_real(dentry));
err = -ETXTBSY;
if (atomic_read(&realinode->i_writecount) < 0)
goto out_drop_write;
}
err = ovl_copy_up(dentry);
if (!err) {
struct inode *winode = NULL;
upperdentry = ovl_dentry_upper(dentry);
if (attr->ia_valid & ATTR_SIZE) {
winode = d_inode(upperdentry);
err = get_write_access(winode);
if (err)
goto out_drop_write;
}
if (attr->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID))
attr->ia_valid &= ~ATTR_MODE;
inode_lock(upperdentry->d_inode);
old_cred = ovl_override_creds(dentry->d_sb);
err = notify_change(upperdentry, attr, NULL);
revert_creds(old_cred);
if (!err)
ovl_copyattr(upperdentry->d_inode, dentry->d_inode);
inode_unlock(upperdentry->d_inode);
if (winode)
put_write_access(winode);
}
out_drop_write:
ovl_drop_write(dentry);
out:
return err;
}
static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry,
struct kstat *stat)
{
struct path realpath;
const struct cred *old_cred;
int err;
ovl_path_real(dentry, &realpath);
old_cred = ovl_override_creds(dentry->d_sb);
err = vfs_getattr(&realpath, stat);
revert_creds(old_cred);
return err;
}
int ovl_permission(struct inode *inode, int mask)
{
bool is_upper;
struct inode *realinode = ovl_inode_real(inode, &is_upper);
const struct cred *old_cred;
int err;
/* Careful in RCU walk mode */
if (!realinode) {
WARN_ON(!(mask & MAY_NOT_BLOCK));
return -ECHILD;
}
/*
* Check overlay inode with the creds of task and underlying inode
* with creds of mounter
*/
err = generic_permission(inode, mask);
if (err)
return err;
old_cred = ovl_override_creds(inode->i_sb);
if (!is_upper && !special_file(realinode->i_mode) && mask & MAY_WRITE) {
mask &= ~(MAY_WRITE | MAY_APPEND);
/* Make sure mounter can read file for copy up later */
mask |= MAY_READ;
}
err = inode_permission(realinode, mask);
revert_creds(old_cred);
return err;
}
static const char *ovl_get_link(struct dentry *dentry,
struct inode *inode,
struct delayed_call *done)
{
struct dentry *realdentry;
struct inode *realinode;
const struct cred *old_cred;
const char *p;
if (!dentry)
return ERR_PTR(-ECHILD);
realdentry = ovl_dentry_real(dentry);
realinode = realdentry->d_inode;
if (WARN_ON(!realinode->i_op->get_link))
return ERR_PTR(-EPERM);
old_cred = ovl_override_creds(dentry->d_sb);
p = realinode->i_op->get_link(realdentry, realinode, done);
revert_creds(old_cred);
return p;
}
static int ovl_readlink(struct dentry *dentry, char __user *buf, int bufsiz)
{
struct path realpath;
struct inode *realinode;
const struct cred *old_cred;
int err;
ovl_path_real(dentry, &realpath);
realinode = realpath.dentry->d_inode;
if (!realinode->i_op->readlink)
return -EINVAL;
old_cred = ovl_override_creds(dentry->d_sb);
err = realinode->i_op->readlink(realpath.dentry, buf, bufsiz);
revert_creds(old_cred);
return err;
}
static bool ovl_is_private_xattr(const char *name)
{
#define OVL_XATTR_PRE_NAME OVL_XATTR_PREFIX "."
return strncmp(name, OVL_XATTR_PRE_NAME,
sizeof(OVL_XATTR_PRE_NAME) - 1) == 0;
}
int ovl_setxattr(struct dentry *dentry, struct inode *inode,
const char *name, const void *value,
size_t size, int flags)
{
int err;
struct dentry *upperdentry;
const struct cred *old_cred;
err = ovl_want_write(dentry);
if (err)
goto out;
err = ovl_copy_up(dentry);
if (err)
goto out_drop_write;
upperdentry = ovl_dentry_upper(dentry);
old_cred = ovl_override_creds(dentry->d_sb);
err = vfs_setxattr(upperdentry, name, value, size, flags);
revert_creds(old_cred);
out_drop_write:
ovl_drop_write(dentry);
out:
return err;
}
ssize_t ovl_getxattr(struct dentry *dentry, struct inode *inode,
const char *name, void *value, size_t size)
{
struct dentry *realdentry = ovl_dentry_real(dentry);
ssize_t res;
const struct cred *old_cred;
if (ovl_is_private_xattr(name))
return -ENODATA;
old_cred = ovl_override_creds(dentry->d_sb);
res = vfs_getxattr(realdentry, name, value, size);
revert_creds(old_cred);
return res;
}
ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
{
struct dentry *realdentry = ovl_dentry_real(dentry);
ssize_t res;
int off;
const struct cred *old_cred;
old_cred = ovl_override_creds(dentry->d_sb);
res = vfs_listxattr(realdentry, list, size);
revert_creds(old_cred);
if (res <= 0 || size == 0)
return res;
/* filter out private xattrs */
for (off = 0; off < res;) {
char *s = list + off;
size_t slen = strlen(s) + 1;
BUG_ON(off + slen > res);
if (ovl_is_private_xattr(s)) {
res -= slen;
memmove(s, s + slen, res - off);
} else {
off += slen;
}
}
return res;
}
int ovl_removexattr(struct dentry *dentry, const char *name)
{
int err;
struct path realpath;
enum ovl_path_type type = ovl_path_real(dentry, &realpath);
const struct cred *old_cred;
err = ovl_want_write(dentry);
if (err)
goto out;
err = -ENODATA;
if (ovl_is_private_xattr(name))
goto out_drop_write;
if (!OVL_TYPE_UPPER(type)) {
err = vfs_getxattr(realpath.dentry, name, NULL, 0);
if (err < 0)
goto out_drop_write;
err = ovl_copy_up(dentry);
if (err)
goto out_drop_write;
ovl_path_upper(dentry, &realpath);
}
old_cred = ovl_override_creds(dentry->d_sb);
err = vfs_removexattr(realpath.dentry, name);
revert_creds(old_cred);
out_drop_write:
ovl_drop_write(dentry);
out:
return err;
}
struct posix_acl *ovl_get_acl(struct inode *inode, int type)
{
struct inode *realinode = ovl_inode_real(inode, NULL);
const struct cred *old_cred;
struct posix_acl *acl;
if (!IS_POSIXACL(realinode))
return NULL;
if (!realinode->i_op->get_acl)
return NULL;
old_cred = ovl_override_creds(inode->i_sb);
acl = realinode->i_op->get_acl(realinode, type);
revert_creds(old_cred);
return acl;
}
static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type,
struct dentry *realdentry)
{
if (OVL_TYPE_UPPER(type))
return false;
if (special_file(realdentry->d_inode->i_mode))
return false;
if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC))
return false;
return true;
}
int ovl_open_maybe_copy_up(struct dentry *dentry, unsigned int file_flags)
{
int err = 0;
struct path realpath;
enum ovl_path_type type;
type = ovl_path_real(dentry, &realpath);
if (ovl_open_need_copy_up(file_flags, type, realpath.dentry)) {
err = ovl_want_write(dentry);
if (!err) {
if (file_flags & O_TRUNC)
err = ovl_copy_up_truncate(dentry);
else
err = ovl_copy_up(dentry);
ovl_drop_write(dentry);
}
}
return err;
}
int ovl_update_time(struct inode *inode, struct timespec *ts, int flags)
{
struct dentry *alias;
struct path upperpath;
if (!(flags & S_ATIME))
return 0;
alias = d_find_any_alias(inode);
if (!alias)
return 0;
ovl_path_upper(alias, &upperpath);
if (upperpath.dentry) {
touch_atime(&upperpath);
inode->i_atime = d_inode(upperpath.dentry)->i_atime;
}
dput(alias);
return 0;
}
static const struct inode_operations ovl_file_inode_operations = {
.setattr = ovl_setattr,
.permission = ovl_permission,
.getattr = ovl_getattr,
.setxattr = generic_setxattr,
.getxattr = ovl_getxattr,
.listxattr = ovl_listxattr,
.removexattr = ovl_removexattr,
.get_acl = ovl_get_acl,
.update_time = ovl_update_time,
};
static const struct inode_operations ovl_symlink_inode_operations = {
.setattr = ovl_setattr,
.get_link = ovl_get_link,
.readlink = ovl_readlink,
.getattr = ovl_getattr,
.setxattr = generic_setxattr,
.getxattr = ovl_getxattr,
.listxattr = ovl_listxattr,
.removexattr = ovl_removexattr,
.update_time = ovl_update_time,
};
static void ovl_fill_inode(struct inode *inode, umode_t mode)
{
inode->i_ino = get_next_ino();
inode->i_mode = mode;
inode->i_flags |= S_NOCMTIME;
mode &= S_IFMT;
switch (mode) {
case S_IFDIR:
inode->i_op = &ovl_dir_inode_operations;
inode->i_fop = &ovl_dir_operations;
break;
case S_IFLNK:
inode->i_op = &ovl_symlink_inode_operations;
break;
default:
WARN(1, "illegal file type: %i\n", mode);
/* Fall through */
case S_IFREG:
case S_IFSOCK:
case S_IFBLK:
case S_IFCHR:
case S_IFIFO:
inode->i_op = &ovl_file_inode_operations;
break;
}
}
struct inode *ovl_new_inode(struct super_block *sb, umode_t mode)
{
struct inode *inode;
inode = new_inode(sb);
if (inode)
ovl_fill_inode(inode, mode);
return inode;
}
static int ovl_inode_test(struct inode *inode, void *data)
{
return ovl_inode_real(inode, NULL) == data;
}
static int ovl_inode_set(struct inode *inode, void *data)
{
inode->i_private = (void *) (((unsigned long) data) | OVL_ISUPPER_MASK);
return 0;
}
struct inode *ovl_get_inode(struct super_block *sb, struct inode *realinode)
{
struct inode *inode;
inode = iget5_locked(sb, (unsigned long) realinode,
ovl_inode_test, ovl_inode_set, realinode);
if (inode && inode->i_state & I_NEW) {
ovl_fill_inode(inode, realinode->i_mode);
set_nlink(inode, realinode->i_nlink);
unlock_new_inode(inode);
}
return inode;
}