[03/11] audit: Fix possible tagging failures
diff mbox series

Message ID 20180904160632.21210-4-jack@suse.cz
State New
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Series
  • audit: Fix various races when tagging and untagging mounts
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Commit Message

Jan Kara Sept. 4, 2018, 4:06 p.m. UTC
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a chunk that is no longer valid one and will soon be destroyed.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.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 kernel/audit_tree.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

Patch
diff mbox series

diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
index 8a74b468b666..c194dbd53753 100644
--- a/kernel/audit_tree.c
+++ b/kernel/audit_tree.c
@@ -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;