Re: [PATCH v2] btrfs: Fix btrfs_find_create_tree_block() testing

[Dan Carpenter <dan.carpenter@oracle.com>]

On Tue, Dec 03, 2019 at 07:40:39PM +0100, David Sterba wrote:
> On Tue, Dec 03, 2019 at 02:24:58PM +0300, Dan Carpenter wrote:
> > The btrfs_find_create_tree_block() uses alloc_test_extent_buffer() for
> > testing and alloc_extent_buffer() for production.  The problem is that
> > the test code returns NULL and the production code returns error
> > pointers.  The callers only check for error pointers.
> > 
> > I have changed alloc_test_extent_buffer() to return error pointers and
> > updated the two callers which use it directly.
> > 
> > Fixes: faa2dbf004e8 ("Btrfs: add sanity tests for new qgroup accounting code")
> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> 
> I edited the changelog because btrfs_find_create_tree_block is
> misleading and seems to be unrelated to the actual fix that's just for
> alloc_test_extent_buffer. Patch added to misc-next, thanks.

The bug is in btrfs_find_create_tree_block()

fs/btrfs/disk-io.c
  1046  struct extent_buffer *btrfs_find_create_tree_block(
  1047                                                  struct btrfs_fs_info *fs_info,
  1048                                                  u64 bytenr)
  1049  {
  1050          if (btrfs_is_testing(fs_info))
  1051                  return alloc_test_extent_buffer(fs_info, bytenr);
                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
NULL

  1052          return alloc_extent_buffer(fs_info, bytenr);
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Error pointers.

  1053  }

None of the callers of btrfs_find_create_tree_block() check for NULL.

regards,
dan carpenter