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>

1 files changed, 5 insertions, 2 deletions

diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index c91babc6aa4b..c6bfa86e2f22 100644
--- 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]);