audit: clean up refcounting in audit-tree

Drop the initial reference by fsnotify_init_mark early instead of
audit_tree_freeing_mark() at destroy time.

In the cases we destroy the mark before we drop the initial reference we need to
get rid of the get_mark that balances the put_mark in audit_tree_freeing_mark().

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

1 files changed, 9 insertions, 3 deletions

diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
index 2b2ffff9eca2..ed206fd88cca 100644
--- a/kernel/audit_tree.c
+++ b/kernel/audit_tree.c
@@ -292,6 +292,7 @@ static void untag_chunk(struct node *p)
         spin_unlock(&hash_lock);
         spin_unlock(&entry->lock);
         fsnotify_destroy_mark(entry);
+        fsnotify_put_mark(&new->mark);  /* drop initial reference */
         goto out;
 
 Fallback:
@@ -330,7 +331,6 @@ static int create_chunk(struct inode *inode, struct audit_tree *tree)
                 spin_unlock(&hash_lock);
                 chunk->dead = 1;
                 spin_unlock(&entry->lock);
-                fsnotify_get_mark(entry);
                 fsnotify_destroy_mark(entry);
                 fsnotify_put_mark(entry);
                 return 0;
@@ -346,6 +346,7 @@ static int create_chunk(struct inode *inode, struct audit_tree *tree)
         insert_hash(chunk);
         spin_unlock(&hash_lock);
         spin_unlock(&entry->lock);
+        fsnotify_put_mark(entry);       /* drop initial reference */
         return 0;
 }
 
@@ -411,7 +412,6 @@ static int tag_chunk(struct inode *inode, struct audit_tree *tree)
                 spin_unlock(&chunk_entry->lock);
                 spin_unlock(&old_entry->lock);
 
-                fsnotify_get_mark(chunk_entry);
                 fsnotify_destroy_mark(chunk_entry);
 
                 fsnotify_put_mark(chunk_entry);
@@ -444,6 +444,7 @@ static int tag_chunk(struct inode *inode, struct audit_tree *tree)
         spin_unlock(&chunk_entry->lock);
         spin_unlock(&old_entry->lock);
         fsnotify_destroy_mark(old_entry);
+        fsnotify_put_mark(chunk_entry); /* drop initial reference */
         fsnotify_put_mark(old_entry); /* pair to fsnotify_find mark_entry */
         return 0;
 }
@@ -915,7 +916,12 @@ static void audit_tree_freeing_mark(struct fsnotify_mark *entry, struct fsnotify
         struct audit_chunk *chunk = container_of(entry, struct audit_chunk, mark);
 
         evict_chunk(chunk);
-        fsnotify_put_mark(entry);
+
+        /*
+         * We are guaranteed to have at least one reference to the mark from
+         * either the inode or the caller of fsnotify_destroy_mark().
+         */
+        BUG_ON(atomic_read(&entry->refcnt) < 1);
 }
 
 static bool audit_tree_send_event(struct fsnotify_group *group, struct inode *inode,