Re: [PATCH 12/13] ext4: send folios that cover a wraparound to the buffer_head path

[sashiko-bot@kernel.org]

> ext4_mpage_readpages() puts a whole folio into a bio with a single
> crypt context, taken from the position of the folio, and blk-crypto
> increments the data unit number for each data unit that follows in
> the bio.
> 
> By contrast, fscrypt truncates the data unit numbers to 32 bits for
> IV_INO_LBLK_32, the only supported IV generation method whose data
> unit numbers wrap around within a file.
> 
> The blocks after a wraparound inside a folio are then en/decrypted
> with IVs of 2^32 + i instead of i.  fscrypt_mergeable_bio() only runs
> between folios, so nothing catches this.
> 
> This is reachable even without a block size larger than the page
> size: when a filesystem is mounted without the encrypt feature,
> [ ... ]
> merges those bios back together.
> 
> Fixes: 709f0f1f1bf5 ("ext4: add checks for large folio incompatibilities when BS > PS")
> Cc: stable@vger.kernel.org # v6.19+
> Signed-off-by: Baokun Li <libaokun@linux.alibaba.com>

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

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261011170958.1759230-1-libaokun@linux.alibaba.com?part=12