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audit: Fix possible tagging failures 

Audit tree code is replacing marks attached to inodes in non-atomic way.
Thus fsnotify_find_mark() in tag_chunk() may find a mark that belongs to
a chunk that is no longer valid one and will soon be destroyed. Tags
added to such chunk will be simply lost.

Fix the problem by making sure old mark is marked as going away (through
fsnotify_detach_mark()) before dropping mark_mutex and thus in an atomic
way wrt tag_chunk(). Note that this does not fix the problem completely
as if tag_chunk() finds a mark that is going away, it fails with
-ENOENT. But at least the failure is not silent and currently there's no
way to search for another fsnotify mark attached to the inode. We'll fix
this problem in later patch.

Reviewed-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Paul Moore <paul@paul-moore.com>
This commit is contained in:
Jan Kara 2018-11-12 09:54:48 -05:00 committed by Paul Moore
parent a5789b07b3
commit b1e4603b92
1 changed files with 10 additions and 7 deletions
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17
kernel/audit_tree.c
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@ -278,8 +278,9 @@ static void untag_chunk(struct node *p)
list_del_init(&p->list);
list_del_rcu(&chunk->hash);
spin_unlock(&hash_lock);
fsnotify_detach_mark(entry);
mutex_unlock(&entry->group->mark_mutex);
fsnotify_destroy_mark(entry, audit_tree_group);
fsnotify_free_mark(entry);
goto out;
}
@ -320,8 +321,9 @@ static void untag_chunk(struct node *p)
list_for_each_entry(owner, &new->trees, same_root)
owner->root = new;
spin_unlock(&hash_lock);
fsnotify_detach_mark(entry);
mutex_unlock(&entry->group->mark_mutex);
fsnotify_destroy_mark(entry, audit_tree_group);
fsnotify_free_mark(entry);
fsnotify_put_mark(&new->mark); /* drop initial reference */
goto out;
@ -364,8 +366,9 @@ static int create_chunk(struct inode *inode, struct audit_tree *tree)
if (tree->goner) {
spin_unlock(&hash_lock);
chunk->dead = 1;
fsnotify_detach_mark(entry);
mutex_unlock(&audit_tree_group->mark_mutex);
fsnotify_destroy_mark(entry, audit_tree_group);
fsnotify_free_mark(entry);
fsnotify_put_mark(entry);
return 0;
}
@ -446,10 +449,9 @@ static int tag_chunk(struct inode *inode, struct audit_tree *tree)
if (tree->goner) {
spin_unlock(&hash_lock);
chunk->dead = 1;
fsnotify_detach_mark(chunk_entry);
mutex_unlock(&audit_tree_group->mark_mutex);
fsnotify_destroy_mark(chunk_entry, audit_tree_group);
fsnotify_free_mark(chunk_entry);
fsnotify_put_mark(chunk_entry);
fsnotify_put_mark(old_entry);
return 0;
@ -477,8 +479,9 @@ static int tag_chunk(struct inode *inode, struct audit_tree *tree)
list_add(&tree->same_root, &chunk->trees);
}
spin_unlock(&hash_lock);
fsnotify_detach_mark(old_entry);
mutex_unlock(&audit_tree_group->mark_mutex);
fsnotify_destroy_mark(old_entry, audit_tree_group);
fsnotify_free_mark(old_entry);
fsnotify_put_mark(chunk_entry); /* drop initial reference */
fsnotify_put_mark(old_entry); /* pair to fsnotify_find mark_entry */
return 0;