Re: [PATCH v2 6.1] erofs: Fix the slab-out-of-bounds in drop_buffers()

[Gao Xiang <hsiangkao@linux.alibaba.com>]

On 2026/3/23 21:59, Denis Arefev wrote:
> commit ce529cc25b184e93397b94a8a322128fc0095cbb upstream.
> 
> This was accidentally fixed in commit ce529cc25b18, but it's not possible
> to accept all the changes, due to the lack of large folios support for
> Linux 6.1 kernels, so this is only the actual bug fix that's needed.
> 
> [Background]
> 
> Syzbot reported that a KASAN slab-out-of-bounds bug was discovered in
> the drop_buffers() function [1].
> 
> The root cause is that erofs_raw_access_aops does not define .release_folio
> and .invalidate_folio. When using iomap-based operations, folio->private
> may contain iomap-specific data rather than buffer_heads. Without special
> handlers, the kernel may fall back to generic functions (such as
> drop_buffers), which incorrectly treat folio->private as a list of
> buffer_head structures, leading to incorrect memory interpretation and
> out-of-bounds access.
> 
> Fix this by explicitly setting .release_folio and .invalidate_folio to the
> values of iomap_release_folio and iomap_invalidate_folio, respectively.
> 
> [1] https://syzkaller.appspot.com/x/report.txt?x=12e5a142580000
> 
> Fixes: 7479c505b4ab ("fs: Convert iomap_readpage to iomap_read_folio")
> Reported-by: syzbot+5b886a2e03529dbcef81@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?id=c6aeabd0c4ad2466f63a274faf2a123103f8fbf7
> Signed-off-by: Denis Arefev <arefev@swemel.ru>

Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>

Thanks,
Gao Xiang