Re: [PATCH] debugfs: byteswap dirsearch dirent buf on big endian systems

[Brian Foster <bfoster@redhat.com>]

On Thu, Jan 23, 2025 at 08:52:11AM -0500, Brian Foster wrote:
> fstests test ext4/048 fails on big endian systems due to broken
> debugfs dirsearch functionality. On an s390x system and 4k block
> size, the dirsearch command seems to hang indefinitely. On the same
> system with a 1k block size, the command fails to locate an existing
> entry and causes the test to fail due to unexpected results.
> 
> The cause of the dirsearch failure is lack of byte swapping of the
> on-disk (little endian) dirent buffer before attempting to iterate
> entries in the given block. This leads to garbage record and name
> length values, for example. To resolve this problem, byte swap the
> directory buffer on big endian systems.
> 
> Signed-off-by: Brian Foster <bfoster@redhat.com>
> ---
> 
> Hi all,
> 
> I'm not terribly familiar with this code, but this fixes the test and
> doesn't show any regressions from fstests runs on big or little endian
> systems. Thanks.
> 

Ping... curious if anybody has thoughts on this for dirsearch on big
endian? Thanks!

Brian

> Brian
> 
>  debugfs/htree.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/debugfs/htree.c b/debugfs/htree.c
> index a1008150..4ea8f30b 100644
> --- a/debugfs/htree.c
> +++ b/debugfs/htree.c
> @@ -482,6 +482,12 @@ static int search_dir_block(ext2_filsys fs, blk64_t *blocknr,
>  		return BLOCK_ABORT;
>  	}
>  
> +#ifdef WORDS_BIGENDIAN
> +	errcode = ext2fs_dirent_swab_in(fs, p->buf, 0);
> +	if (errcode)
> +		return BLOCK_ABORT;
> +#endif
> +
>  	while (offset < fs->blocksize) {
>  		dirent = (struct ext2_dir_entry *) (p->buf + offset);
>  		errcode = ext2fs_get_rec_len(fs, dirent, &rec_len);
> -- 
> 2.47.1
> 
>