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

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Message-ID: <CAGXu5j+AZYrnC-fvxseLVJqeJh5ggOiT9=PUXNweZZbmVy7yWQ@mail.gmail.com>
Date:	Tue, 14 Jun 2016 11:33:55 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Heinrich Schuchardt <xypron.glpk@....de>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Don Zickus <dzickus@...hat.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Dave Young <dyoung@...hat.com>,
	Hugh Dickins <hughd@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Daniel Cashman <dcashman@...gle.com>, Willy Tarreau <w@....eu>,
	Alexei Starovoitov <ast@...mgrid.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Ilya Dryomov <idryomov@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] kernel/sysctl.c: avoid overflow

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

Acked-by: Kees Cook <keescook@...omium.org>

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