dm btree: fix bufio buffer leaks in dm_btree_del() error path

If dm_btree_del()'s call to push_frame() fails, e.g. due to
btree_node_validator finding invalid metadata, the dm_btree_del() error
path must unlock all frames (which have active dm-bufio buffers) that
were pushed onto the del_stack.

Otherwise, dm_bufio_client_destroy() will BUG_ON() because dm-bufio
buffers have leaked, e.g.:
  device-mapper: bufio: leaked buffer 3, hold count 1, list 0

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org

1 files changed, 15 insertions, 1 deletions

diff --git a/drivers/md/persistent-data/dm-btree.c b/drivers/md/persistent-data/dm-btree.c
index 7e5b7f12958a..b1ced58eb5e1 100644
--- a/drivers/md/persistent-data/dm-btree.c
+++ b/drivers/md/persistent-data/dm-btree.c
@@ -257,6 +257,16 @@ static void pop_frame(struct del_stack *s)
         dm_tm_unlock(s->tm, f->b);
 }
 
+static void unlock_all_frames(struct del_stack *s)
+{
+        struct frame *f;
+
+        while (unprocessed_frames(s)) {
+                f = s->spine + s->top--;
+                dm_tm_unlock(s->tm, f->b);
+        }
+}
+
 int dm_btree_del(struct dm_btree_info *info, dm_block_t root)
 {
         int r;
@@ -313,9 +323,13 @@ int dm_btree_del(struct dm_btree_info *info, dm_block_t root)
                         pop_frame(s);
                 }
         }
-
 out:
+        if (r) {
+                /* cleanup all frames of del_stack */
+                unlock_all_frames(s);
+        }
         kfree(s);
+
         return r;
 }
 EXPORT_SYMBOL_GPL(dm_btree_del);