linux-kernel - Re: [PATCH] fs: btrfs: fix potential overflow

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Message-ID: <CAGqmi757Husduwnis_ci_z1Z-6tjCuOHDHt0dx=jBquguzrFbA@mail.gmail.com>
Date:	Sun, 24 Aug 2014 12:44:11 +0300
From:	Timofey Titovets <nefelim4ag@...il.com>
To:	Brian Norris <computersforpeace@...il.com>
Cc:	Chris Mason <clm@...com>, Josef Bacik <jbacik@...com>,
	linux-btrfs <linux-btrfs@...r.kernel.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] fs: btrfs: fix potential overflow

2014-08-24 8:41 GMT+03:00 Brian Norris <computeaboversforpeace@...il.com>:
> It looks like this intended to be 64-bit arithmetic, but it's actually
> performed as 32-bit. Fix that. (Note that 'increment' was being
> initialized twice, so this patch removes one of those.)
>
> Caught by Coverity Scan (CID 1201422).
>
> Signed-off-by: Brian Norris <computersforpeace@...il.com>
> ---
> Untested
>
>  fs/btrfs/scrub.c |   12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
> index b6d198f5181e..b1a8127737b4 100644
> --- a/fs/btrfs/scrub.c
> +++ b/fs/btrfs/scrub.c
> @@ -2320,26 +2320,26 @@ static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx,
>         do_div(nstripes, map->stripe_len);
>         if (map->type & BTRFS_BLOCK_GROUP_RAID0) {
>                 offset = map->stripe_len * num;
> -               increment = map->stripe_len * map->num_stripes;
> +               increment *= map->num_stripes;
>                 mirror_num = 1;
>         } else if (map->type & BTRFS_BLOCK_GROUP_RAID10) {
>                 int factor = map->num_stripes / map->sub_stripes;
>                 offset = map->stripe_len * (num / map->sub_stripes);
> -               increment = map->stripe_len * factor;
> +               increment *= factor;
>                 mirror_num = num % map->sub_stripes + 1;
>         } else if (map->type & BTRFS_BLOCK_GROUP_RAID1) {
> -               increment = map->stripe_len;
> +               increment *= 1;
Why? I think multiple by one is useless or i miss something?

>                 mirror_num = num % map->num_stripes + 1;
>         } else if (map->type & BTRFS_BLOCK_GROUP_DUP) {
> -               increment = map->stripe_len;
> +               increment *= 1;
Same as above.

>                 mirror_num = num % map->num_stripes + 1;
>         } else if (map->type & (BTRFS_BLOCK_GROUP_RAID5 |
>                                 BTRFS_BLOCK_GROUP_RAID6)) {
>                 get_raid56_logic_offset(physical, num, map, &offset);
> -               increment = map->stripe_len * nr_data_stripes(map);
> +               increment *= nr_data_stripes(map);
>                 mirror_num = 1;
>         } else {
> -               increment = map->stripe_len;
> +               increment *= 1;
Same.
>                 mirror_num = 1;
>         }
>
> --
> 1.7.9.5
>
> --
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-- 
Have a nice day,
Timofey.
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