linux-kernel - Re: [PATCH v2] ext4: fix infinite loop when replaying fast

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Message-ID: <87a5j67aq7.fsf@brahms.olymp>
Date: Thu, 27 Jun 2024 14:53:52 +0100
From: Luis Henriques <luis.henriques@...ux.dev>
To: Theodore Ts'o <tytso@....edu>,  Andreas Dilger <adilger@...ger.ca>
Cc: Zhang Yi <yi.zhang@...weicloud.com>,  Harshad Shirwadkar
 <harshadshirwadkar@...il.com>,  linux-ext4@...r.kernel.org,
  linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] ext4: fix infinite loop when replaying fast_commit

On Wed, May 15 2024, Luis Henriques (SUSE) wrote:

> When doing fast_commit replay an infinite loop may occur due to an
> uninitialized extent_status struct.  ext4_ext_determine_insert_hole() does
> not detect the replay and calls ext4_es_find_extent_range(), which will
> return immediately without initializing the 'es' variable.
>
> Because 'es' contains garbage, an integer overflow may happen causing an
> infinite loop in this function, easily reproducible using fstest generic/039.
>
> This commit fixes this issue by unconditionally initializing the structure
> in function ext4_es_find_extent_range().
>
> Thanks to Zhang Yi, for figuring out the real problem!
>
> Fixes: 8016e29f4362 ("ext4: fast commit recovery path")
> Signed-off-by: Luis Henriques (SUSE) <luis.henriques@...ux.dev>

Gentle ping...  Has this fell through the cracks?

Cheers,
-- 
Luis

> ---
>  fs/ext4/extents_status.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
> index 4a00e2f019d9..3a53dbb85e15 100644
> --- a/fs/ext4/extents_status.c
> +++ b/fs/ext4/extents_status.c
> @@ -310,6 +310,8 @@ void ext4_es_find_extent_range(struct inode *inode,
>  			       ext4_lblk_t lblk, ext4_lblk_t end,
>  			       struct extent_status *es)
>  {
> +	es->es_lblk = es->es_len = es->es_pblk = 0;
> +
>  	if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
>  		return;
>