linux-kernel - Re: [PATCH 1/1] dm-integrity: Remove unreachable code in dm_integrity

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Message-ID: <b4a06abf-eb97-055a-a986-6e629c59ca1b@redhat.com>
Date: Mon, 8 Sep 2025 15:44:59 +0200 (CEST)
From: Mikulas Patocka <mpatocka@...hat.com>
To: Ivan Abramov <i.abramov@...integration.ru>
cc: Alasdair Kergon <agk@...hat.com>, Mike Snitzer <snitzer@...nel.org>, 
    dm-devel@...ts.linux.dev, linux-kernel@...r.kernel.org, 
    lvc-project@...uxtesting.org
Subject: Re: [PATCH 1/1] dm-integrity: Remove unreachable code in
 dm_integrity_ctr()

Hi

What if someone changes it to a larger type later? I think that if this 
branch doesn't do any harm and if it protects us from memory errors 
introduced by future changes, we may let it be there.

But I found another bug when looking at this - the user may set tag size 
up to MAX_TAG_SIZE (that is 0x1a8) and that gets truncated when it is 
assigned in "bi->metadata_size = ic->tag_size". I need to limit 
MAX_TAG_SIZE to 255.

Mikulas


On Mon, 8 Sep 2025, Ivan Abramov wrote:

> Since bi->metadata_size is an unsigned char, it's not practically
> possible for it to be > PAGE_SIZE / 2.
> 
> Thus, remove the corresponding if statement.
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Signed-off-by: Ivan Abramov <i.abramov@...integration.ru>
> ---
>  drivers/md/dm-integrity.c | 5 -----
>  1 file changed, 5 deletions(-)
> 
> diff --git a/drivers/md/dm-integrity.c b/drivers/md/dm-integrity.c
> index efeee0a873c0..b7ad7a5adb56 100644
> --- a/drivers/md/dm-integrity.c
> +++ b/drivers/md/dm-integrity.c
> @@ -4752,11 +4752,6 @@ static int dm_integrity_ctr(struct dm_target *ti, unsigned int argc, char **argv
>  			ti->error = "The integrity profile is smaller than tag size";
>  			goto bad;
>  		}
> -		if ((unsigned long)bi->metadata_size > PAGE_SIZE / 2) {
> -			r = -EINVAL;
> -			ti->error = "Too big tuple size";
> -			goto bad;
> -		}
>  		ic->tuple_size = bi->metadata_size;
>  		if (1 << bi->interval_exp != ic->sectors_per_block << SECTOR_SHIFT) {
>  			r = -EINVAL;
> -- 
> 2.39.5
> 
>