linux-kernel - Re: [PATCH] ext4: fix an off-by-one issue during moving extents

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <sl2tbcoqrlktv23wkiwt7bkqv3aspnvsgijrbjx23b4gr53h6o@oskiuintay3k>
Date: Fri, 12 Sep 2025 16:17:40 +0200
From: Jan Kara <jack@...e.cz>
To: Zhang Yi <yi.zhang@...weicloud.com>
Cc: linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org, 
	linux-kernel@...r.kernel.org, tytso@....edu, adilger.kernel@...ger.ca, jack@...e.cz, 
	yi.zhang@...wei.com, libaokun1@...wei.com, yukuai3@...wei.com, yangerkun@...wei.com
Subject: Re: [PATCH] ext4: fix an off-by-one issue during moving extents

On Fri 12-09-25 18:58:41, Zhang Yi wrote:
> From: Zhang Yi <yi.zhang@...wei.com>
> 
> During the movement of a written extent, mext_page_mkuptodate() is
> called to read data in the range [from, to) into the page cache and to
> update the corresponding buffers. Therefore, we should not wait on any
> buffer whose start offset is >= 'to'. Otherwise, it will return -EIO and
> fail the extents movement.
> 
>  $ for i in `seq 3 -1 0`; \
>    do xfs_io -fs -c "pwrite -b 1024 $((i * 1024)) 1024" /mnt/foo; \
>    done
>  $ umount /mnt && mount /dev/pmem1s /mnt  # drop cache
>  $ e4defrag /mnt/foo
>    e4defrag 1.47.0 (5-Feb-2023)
>    ext4 defragmentation for /mnt/foo
>    [1/1]/mnt/foo:    0%    [ NG ]
>    Success:                       [0/1]
> 
> Fixes: a40759fb16ae ("ext4: remove array of buffer_heads from mext_page_mkuptodate()")
> Signed-off-by: Zhang Yi <yi.zhang@...wei.com>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  fs/ext4/move_extent.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
> index adae3caf175a..4b091c21908f 100644
> --- a/fs/ext4/move_extent.c
> +++ b/fs/ext4/move_extent.c
> @@ -225,7 +225,7 @@ static int mext_page_mkuptodate(struct folio *folio, size_t from, size_t to)
>  	do {
>  		if (bh_offset(bh) + blocksize <= from)
>  			continue;
> -		if (bh_offset(bh) > to)
> +		if (bh_offset(bh) >= to)
>  			break;
>  		wait_on_buffer(bh);
>  		if (buffer_uptodate(bh))
> -- 
> 2.46.1
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR