linux-kernel - Re: [PATCH] hex2bin: fix access beyond string end

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

Date:   Tue, 26 Apr 2022 12:37:08 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Mikulas Patocka <mpatocka@...hat.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Shevchenko <andy@...nel.org>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        device-mapper development <dm-devel@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mike Snitzer <msnitzer@...hat.com>,
        Milan Broz <gmazyland@...il.com>
Subject: Re: [PATCH] hex2bin: fix access beyond string end

On Sun, Apr 24, 2022 at 10:48 PM Mikulas Patocka <mpatocka@...hat.com> wrote:
>
> If we pass too short string to "hex2bin" (and the string size without the
> terminating NUL character is even), "hex2bin" reads one byte after the
> terminating NUL character. This patch fixes it.
>
> Signed-off-by: Mikulas Patocka <mpatocka@...hat.com>
> Cc: stable@...r.kernel.org

You need to provide a Fixes tag.

...

>         while (count--) {
> -               int hi = hex_to_bin(*src++);
> -               int lo = hex_to_bin(*src++);
> +               int hi, lo;
>
> -               if ((hi < 0) || (lo < 0))
> +               hi = hex_to_bin(*src++);
> +               if (hi < 0)
> +                       return -EINVAL;

return hi;

> +               lo = hex_to_bin(*src++);
> +               if (lo < 0)
>                         return -EINVAL;

return lo;

>                 *dst++ = (hi << 4) | lo;

And on top of that it would be nice to understand if we need to
support half-bytes, but in any case it's not a scope of the patch
right now.

-- 
With Best Regards,
Andy Shevchenko