949b9c3d42
So far, POSIX ACLs are using a canonical representation that keeps all ACL entries in a strict order; the ACL_USER and ACL_GROUP entries for specific users and groups are ordered by user and group identifier, respectively. The user-space code provides ACL entries in this order; the kernel verifies that the ACL entry order is correct in posix_acl_valid(). User namespaces allow to arbitrary map user and group identifiers which can cause the ACL_USER and ACL_GROUP entry order to differ between user space and the kernel; posix_acl_valid() would then fail. Work around this by allowing ACL_USER and ACL_GROUP entries to be in any order in the kernel. The effect is only minor: file permission checks will pick the first matching ACL_USER entry, and check all matching ACL_GROUP entries. (The libacl user-space library and getfacl / setfacl tools will not create ACLs with duplicate user or group idenfifiers; they will handle ACLs with entries in an arbitrary order correctly.) Signed-off-by: Andreas Gruenbacher <agruen@linbit.com> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: Theodore Tso <tytso@mit.edu> Cc: Christoph Hellwig <hch@infradead.org> Cc: Andreas Dilger <adilger.kernel@dilger.ca> Cc: Jan Kara <jack@suse.cz> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
485 lines
11 KiB
C
485 lines
11 KiB
C
/*
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* linux/fs/posix_acl.c
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*
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* Copyright (C) 2002 by Andreas Gruenbacher <a.gruenbacher@computer.org>
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*
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* Fixes from William Schumacher incorporated on 15 March 2001.
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* (Reported by Charles Bertsch, <CBertsch@microtest.com>).
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*/
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/*
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* This file contains generic functions for manipulating
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* POSIX 1003.1e draft standard 17 ACLs.
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*/
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#include <linux/kernel.h>
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#include <linux/slab.h>
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#include <linux/atomic.h>
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#include <linux/fs.h>
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#include <linux/sched.h>
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#include <linux/posix_acl.h>
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#include <linux/export.h>
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#include <linux/errno.h>
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struct posix_acl **acl_by_type(struct inode *inode, int type)
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{
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switch (type) {
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case ACL_TYPE_ACCESS:
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return &inode->i_acl;
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case ACL_TYPE_DEFAULT:
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return &inode->i_default_acl;
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default:
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BUG();
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}
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}
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EXPORT_SYMBOL(acl_by_type);
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struct posix_acl *get_cached_acl(struct inode *inode, int type)
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{
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struct posix_acl **p = acl_by_type(inode, type);
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struct posix_acl *acl = ACCESS_ONCE(*p);
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if (acl) {
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spin_lock(&inode->i_lock);
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acl = *p;
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if (acl != ACL_NOT_CACHED)
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acl = posix_acl_dup(acl);
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spin_unlock(&inode->i_lock);
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}
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return acl;
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}
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EXPORT_SYMBOL(get_cached_acl);
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struct posix_acl *get_cached_acl_rcu(struct inode *inode, int type)
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{
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return rcu_dereference(*acl_by_type(inode, type));
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}
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EXPORT_SYMBOL(get_cached_acl_rcu);
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void set_cached_acl(struct inode *inode, int type, struct posix_acl *acl)
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{
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struct posix_acl **p = acl_by_type(inode, type);
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struct posix_acl *old;
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spin_lock(&inode->i_lock);
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old = *p;
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rcu_assign_pointer(*p, posix_acl_dup(acl));
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spin_unlock(&inode->i_lock);
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if (old != ACL_NOT_CACHED)
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posix_acl_release(old);
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}
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EXPORT_SYMBOL(set_cached_acl);
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void forget_cached_acl(struct inode *inode, int type)
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{
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struct posix_acl **p = acl_by_type(inode, type);
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struct posix_acl *old;
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spin_lock(&inode->i_lock);
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old = *p;
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*p = ACL_NOT_CACHED;
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spin_unlock(&inode->i_lock);
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if (old != ACL_NOT_CACHED)
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posix_acl_release(old);
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}
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EXPORT_SYMBOL(forget_cached_acl);
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void forget_all_cached_acls(struct inode *inode)
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{
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struct posix_acl *old_access, *old_default;
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spin_lock(&inode->i_lock);
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old_access = inode->i_acl;
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old_default = inode->i_default_acl;
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inode->i_acl = inode->i_default_acl = ACL_NOT_CACHED;
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spin_unlock(&inode->i_lock);
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if (old_access != ACL_NOT_CACHED)
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posix_acl_release(old_access);
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if (old_default != ACL_NOT_CACHED)
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posix_acl_release(old_default);
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}
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EXPORT_SYMBOL(forget_all_cached_acls);
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/*
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* Init a fresh posix_acl
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*/
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void
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posix_acl_init(struct posix_acl *acl, int count)
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{
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atomic_set(&acl->a_refcount, 1);
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acl->a_count = count;
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}
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EXPORT_SYMBOL(posix_acl_init);
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/*
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* Allocate a new ACL with the specified number of entries.
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*/
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struct posix_acl *
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posix_acl_alloc(int count, gfp_t flags)
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{
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const size_t size = sizeof(struct posix_acl) +
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count * sizeof(struct posix_acl_entry);
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struct posix_acl *acl = kmalloc(size, flags);
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if (acl)
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posix_acl_init(acl, count);
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return acl;
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}
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EXPORT_SYMBOL(posix_acl_alloc);
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/*
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* Clone an ACL.
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*/
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static struct posix_acl *
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posix_acl_clone(const struct posix_acl *acl, gfp_t flags)
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{
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struct posix_acl *clone = NULL;
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if (acl) {
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int size = sizeof(struct posix_acl) + acl->a_count *
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sizeof(struct posix_acl_entry);
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clone = kmemdup(acl, size, flags);
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if (clone)
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atomic_set(&clone->a_refcount, 1);
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}
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return clone;
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}
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/*
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* Check if an acl is valid. Returns 0 if it is, or -E... otherwise.
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*/
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int
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posix_acl_valid(const struct posix_acl *acl)
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{
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const struct posix_acl_entry *pa, *pe;
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int state = ACL_USER_OBJ;
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int needs_mask = 0;
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FOREACH_ACL_ENTRY(pa, acl, pe) {
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if (pa->e_perm & ~(ACL_READ|ACL_WRITE|ACL_EXECUTE))
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return -EINVAL;
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switch (pa->e_tag) {
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case ACL_USER_OBJ:
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if (state == ACL_USER_OBJ) {
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state = ACL_USER;
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break;
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}
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return -EINVAL;
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case ACL_USER:
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if (state != ACL_USER)
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return -EINVAL;
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if (!uid_valid(pa->e_uid))
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return -EINVAL;
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needs_mask = 1;
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break;
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case ACL_GROUP_OBJ:
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if (state == ACL_USER) {
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state = ACL_GROUP;
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break;
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}
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return -EINVAL;
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case ACL_GROUP:
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if (state != ACL_GROUP)
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return -EINVAL;
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if (!gid_valid(pa->e_gid))
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return -EINVAL;
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needs_mask = 1;
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break;
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case ACL_MASK:
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if (state != ACL_GROUP)
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return -EINVAL;
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state = ACL_OTHER;
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break;
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case ACL_OTHER:
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if (state == ACL_OTHER ||
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(state == ACL_GROUP && !needs_mask)) {
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state = 0;
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break;
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}
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return -EINVAL;
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default:
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return -EINVAL;
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}
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}
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if (state == 0)
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return 0;
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return -EINVAL;
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}
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EXPORT_SYMBOL(posix_acl_valid);
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/*
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* Returns 0 if the acl can be exactly represented in the traditional
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* file mode permission bits, or else 1. Returns -E... on error.
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*/
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int
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posix_acl_equiv_mode(const struct posix_acl *acl, umode_t *mode_p)
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{
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const struct posix_acl_entry *pa, *pe;
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umode_t mode = 0;
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int not_equiv = 0;
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FOREACH_ACL_ENTRY(pa, acl, pe) {
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switch (pa->e_tag) {
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case ACL_USER_OBJ:
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mode |= (pa->e_perm & S_IRWXO) << 6;
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break;
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case ACL_GROUP_OBJ:
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mode |= (pa->e_perm & S_IRWXO) << 3;
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break;
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case ACL_OTHER:
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mode |= pa->e_perm & S_IRWXO;
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break;
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case ACL_MASK:
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mode = (mode & ~S_IRWXG) |
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((pa->e_perm & S_IRWXO) << 3);
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not_equiv = 1;
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break;
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case ACL_USER:
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case ACL_GROUP:
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not_equiv = 1;
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break;
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default:
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return -EINVAL;
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}
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}
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if (mode_p)
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*mode_p = (*mode_p & ~S_IRWXUGO) | mode;
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return not_equiv;
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}
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EXPORT_SYMBOL(posix_acl_equiv_mode);
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/*
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* Create an ACL representing the file mode permission bits of an inode.
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*/
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struct posix_acl *
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posix_acl_from_mode(umode_t mode, gfp_t flags)
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{
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struct posix_acl *acl = posix_acl_alloc(3, flags);
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if (!acl)
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return ERR_PTR(-ENOMEM);
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acl->a_entries[0].e_tag = ACL_USER_OBJ;
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acl->a_entries[0].e_perm = (mode & S_IRWXU) >> 6;
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acl->a_entries[1].e_tag = ACL_GROUP_OBJ;
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acl->a_entries[1].e_perm = (mode & S_IRWXG) >> 3;
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acl->a_entries[2].e_tag = ACL_OTHER;
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acl->a_entries[2].e_perm = (mode & S_IRWXO);
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return acl;
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}
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EXPORT_SYMBOL(posix_acl_from_mode);
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/*
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* Return 0 if current is granted want access to the inode
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* by the acl. Returns -E... otherwise.
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*/
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int
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posix_acl_permission(struct inode *inode, const struct posix_acl *acl, int want)
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{
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const struct posix_acl_entry *pa, *pe, *mask_obj;
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int found = 0;
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want &= MAY_READ | MAY_WRITE | MAY_EXEC | MAY_NOT_BLOCK;
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FOREACH_ACL_ENTRY(pa, acl, pe) {
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switch(pa->e_tag) {
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case ACL_USER_OBJ:
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/* (May have been checked already) */
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if (uid_eq(inode->i_uid, current_fsuid()))
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goto check_perm;
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break;
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case ACL_USER:
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if (uid_eq(pa->e_uid, current_fsuid()))
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goto mask;
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break;
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case ACL_GROUP_OBJ:
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if (in_group_p(inode->i_gid)) {
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found = 1;
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if ((pa->e_perm & want) == want)
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goto mask;
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}
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break;
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case ACL_GROUP:
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if (in_group_p(pa->e_gid)) {
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found = 1;
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if ((pa->e_perm & want) == want)
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goto mask;
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}
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break;
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case ACL_MASK:
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break;
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case ACL_OTHER:
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if (found)
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return -EACCES;
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else
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goto check_perm;
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default:
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return -EIO;
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}
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}
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return -EIO;
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mask:
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for (mask_obj = pa+1; mask_obj != pe; mask_obj++) {
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if (mask_obj->e_tag == ACL_MASK) {
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if ((pa->e_perm & mask_obj->e_perm & want) == want)
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return 0;
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return -EACCES;
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}
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}
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check_perm:
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if ((pa->e_perm & want) == want)
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return 0;
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return -EACCES;
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}
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/*
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* Modify acl when creating a new inode. The caller must ensure the acl is
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* only referenced once.
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*
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* mode_p initially must contain the mode parameter to the open() / creat()
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* system calls. All permissions that are not granted by the acl are removed.
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* The permissions in the acl are changed to reflect the mode_p parameter.
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*/
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static int posix_acl_create_masq(struct posix_acl *acl, umode_t *mode_p)
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{
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struct posix_acl_entry *pa, *pe;
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struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
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umode_t mode = *mode_p;
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int not_equiv = 0;
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/* assert(atomic_read(acl->a_refcount) == 1); */
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FOREACH_ACL_ENTRY(pa, acl, pe) {
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switch(pa->e_tag) {
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case ACL_USER_OBJ:
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pa->e_perm &= (mode >> 6) | ~S_IRWXO;
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mode &= (pa->e_perm << 6) | ~S_IRWXU;
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break;
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case ACL_USER:
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case ACL_GROUP:
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not_equiv = 1;
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break;
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case ACL_GROUP_OBJ:
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group_obj = pa;
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break;
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case ACL_OTHER:
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pa->e_perm &= mode | ~S_IRWXO;
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mode &= pa->e_perm | ~S_IRWXO;
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break;
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case ACL_MASK:
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mask_obj = pa;
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not_equiv = 1;
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break;
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default:
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return -EIO;
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}
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}
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if (mask_obj) {
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mask_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
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mode &= (mask_obj->e_perm << 3) | ~S_IRWXG;
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} else {
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if (!group_obj)
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return -EIO;
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group_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
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mode &= (group_obj->e_perm << 3) | ~S_IRWXG;
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}
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*mode_p = (*mode_p & ~S_IRWXUGO) | mode;
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return not_equiv;
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}
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/*
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* Modify the ACL for the chmod syscall.
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*/
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static int posix_acl_chmod_masq(struct posix_acl *acl, umode_t mode)
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{
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struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
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struct posix_acl_entry *pa, *pe;
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/* assert(atomic_read(acl->a_refcount) == 1); */
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FOREACH_ACL_ENTRY(pa, acl, pe) {
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switch(pa->e_tag) {
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case ACL_USER_OBJ:
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pa->e_perm = (mode & S_IRWXU) >> 6;
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break;
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case ACL_USER:
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case ACL_GROUP:
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break;
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case ACL_GROUP_OBJ:
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group_obj = pa;
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break;
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case ACL_MASK:
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mask_obj = pa;
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break;
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case ACL_OTHER:
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pa->e_perm = (mode & S_IRWXO);
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break;
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default:
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return -EIO;
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}
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}
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if (mask_obj) {
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mask_obj->e_perm = (mode & S_IRWXG) >> 3;
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} else {
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if (!group_obj)
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return -EIO;
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group_obj->e_perm = (mode & S_IRWXG) >> 3;
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}
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return 0;
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}
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int
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posix_acl_create(struct posix_acl **acl, gfp_t gfp, umode_t *mode_p)
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{
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struct posix_acl *clone = posix_acl_clone(*acl, gfp);
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int err = -ENOMEM;
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if (clone) {
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err = posix_acl_create_masq(clone, mode_p);
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if (err < 0) {
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posix_acl_release(clone);
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clone = NULL;
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}
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}
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posix_acl_release(*acl);
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*acl = clone;
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return err;
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}
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EXPORT_SYMBOL(posix_acl_create);
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int
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posix_acl_chmod(struct posix_acl **acl, gfp_t gfp, umode_t mode)
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{
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struct posix_acl *clone = posix_acl_clone(*acl, gfp);
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int err = -ENOMEM;
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if (clone) {
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err = posix_acl_chmod_masq(clone, mode);
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if (err) {
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posix_acl_release(clone);
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clone = NULL;
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}
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}
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posix_acl_release(*acl);
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*acl = clone;
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return err;
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}
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EXPORT_SYMBOL(posix_acl_chmod);
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