Btrfs: fix NULL pointer dereference in log_dir_items

0, 1 and <0 can be returned by btrfs_next_leaf(), and when <0 is
returned, path->nodes[0] could be NULL, log_dir_items lacks such a
check for <0 and we may run into a null pointer dereference panic.

Fixes: e02119d5a7b4 ("Btrfs: Add a write ahead tree log to optimize synchronous operations")
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Liu Bo <bo.liu@linux.alibaba.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index c91babc6aa4b3f1ae8e83074db6f64264369ee52..c6bfa86e2f228ef27965e78faabd2d44151425b9 100644 (file)
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -3520,8 +3520,11 @@ static noinline int log_dir_items(struct btrfs_trans_handle *trans,
                 * from this directory and from this transaction
                 */
                ret = btrfs_next_leaf(root, path);
-               if (ret == 1) {
-                       last_offset = (u64)-1;
+               if (ret) {
+                       if (ret == 1)
+                               last_offset = (u64)-1;
+                       else
+                               err = ret;
                        goto done;
                }
                btrfs_item_key_to_cpu(path->nodes[0], &tmp, path->slots[0]);