[dm-devel] [PATCH] hex2bin: fix access beyond string end

[Andy Shevchenko]

On Sun, Apr 24, 2022 at 10:48 PM Mikulas Patocka <mpatocka at redhat.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 at redhat.com>
> Cc: stable at vger.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