Re: [PATCH] ext4: do not accept rec_len 0 for block sizes below 64k

[sashiko-bot@kernel.org]

> From: Hengyu Liang <hengyul@cs.unc.edu>
> 
> Commit afa6d5a16bf2 ("ext4: remove PAGE_SIZE checks for rec_len
> conversion") made ext4_rec_len_from_disk() read a rec_len of 0 as "this
> entry covers the whole block" for every block size.
> 
> However, this special value only exists for block sizes of 64k and
> more. With smaller blocks, a rec_len of 0 means that the directory
> block is corrupted. As of now, a directory block that has been
> overwritten with zeroes is treated as an empty block. The kernel no
> longer reports the corruption and can store new entries in that block,
> while e2fsck still reports the block as corrupted.
> 
> The issue can be reproduced on a file system without metadata_csum:
> 
> [ ... ]
> unchanged when the block size is below 64k, as e2fsprogs does.
> 
> Fixes: afa6d5a16bf2 ("ext4: remove PAGE_SIZE checks for rec_len conversion")
> Cc: stable@vger.kernel.org
> Signed-off-by: Hengyu Liang <hengyul@cs.unc.edu>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20261006111546.3252481-1-hengyul@cs.unc.edu?part=1