Re: [PATCH 1/1] kernel/sysctl.c: avoid overflow

[Kees Cook]

On Fri, Jun 10, 2016 at 6:33 PM, Heinrich Schuchardt <xypron.glpk@xxxxxx> wrote:
> An undetected overflow may occur in do_proc_dointvec_minmax_conv_param.
>
> Signed-off-by: Heinrich Schuchardt <xypron.glpk@xxxxxx>

Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>

Thanks for the fix!

-Kees

> ---
>  kernel/sysctl.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 35f0dcb..a9e7be3 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -2313,7 +2313,17 @@ static int do_proc_dointvec_minmax_conv(bool *negp, unsigned long *lvalp,
>  {
>         struct do_proc_dointvec_minmax_conv_param *param = data;
>         if (write) {
> -               int val = *negp ? -*lvalp : *lvalp;
> +               int val;
> +
> +               if (*negp) {
> +                       if (*lvalp > (unsigned long) INT_MAX + 1)
> +                               return -EINVAL;
> +                       val = -*lvalp;
> +               } else {
> +                       if (*lvalp > (unsigned long) INT_MAX)
> +                               return -EINVAL;
> +                       val = *lvalp;
> +               }
>                 if ((param->min && *param->min > val) ||
>                     (param->max && *param->max < val))
>                         return -EINVAL;
> --
> 2.1.4
>



-- 
Kees Cook
Chrome OS & Brillo Security