linux-kernel - Re: [PATCH] Yama: handle 32-bit userspace prctl

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Message-ID: <CAGXu5jLwhXtZj1KZjV-P6ugDF0uWzYfWKq-eSfwgiGqWYc3E4w@mail.gmail.com>
Date:	Wed, 5 Sep 2012 14:41:36 -0700
From:	Kees Cook <keescook@...omium.org>
To:	James Morris <james.l.morris@...cle.com>
Cc:	Kees Cook <keescook@...omium.org>,
	John Johansen <john.johansen@...onical.com>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Yama: handle 32-bit userspace prctl

Hi James,

Any chance this can get into security-next as well? It'll need to go
back to stable, but it's a small enough corner-case that I don't mind
it not landing in 3.6 directly. I'm happy if it gets into 3.6.x stable
at some point.

Thanks!

-Kees

On Mon, Aug 27, 2012 at 11:38 AM, Kees Cook <keescook@...omium.org> wrote:
> When running a 64-bit kernel and receiving prctls from a 32-bit
> userspace, the "-1" used as an unsigned long will end up being
> misdetected. The kernel is looking for 0xffffffffffffffff instead of
> 0xffffffff. Since prctl lacks a distinct compat interface, Yama needs
> to handle this translation itself. As such, support either value as
> meaning PR_SET_PTRACER_ANY, to avoid breaking the ABI for 64-bit.
>
> Signed-off-by: Kees Cook <keescook@...omium.org>
> Cc: stable@...r.kernel.org
> ---
>  security/yama/yama_lsm.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c
> index 0cc99a3..dcd6178 100644
> --- a/security/yama/yama_lsm.c
> +++ b/security/yama/yama_lsm.c
> @@ -143,7 +143,7 @@ static int yama_task_prctl(int option, unsigned long arg2, unsigned long arg3,
>                 if (arg2 == 0) {
>                         yama_ptracer_del(NULL, myself);
>                         rc = 0;
> -               } else if (arg2 == PR_SET_PTRACER_ANY) {
> +               } else if (arg2 == PR_SET_PTRACER_ANY || (int)arg2 == -1) {
>                         rc = yama_ptracer_add(NULL, myself);
>                 } else {
>                         struct task_struct *tracer;
> --
> 1.7.0.4
>
>
> --
> Kees Cook
> Chrome OS Security



-- 
Kees Cook
Chrome OS Security
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