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

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Date:	Wed, 05 Sep 2012 15:06:03 -0700
From:	John Johansen <john.johansen@...onical.com>
To:	Kees Cook <keescook@...omium.org>
CC:	linux-kernel@...r.kernel.org,
	James Morris <james.l.morris@...cle.com>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	linux-security-module@...r.kernel.org
Subject: Re: [PATCH] Yama: handle 32-bit userspace prctl

On 08/27/2012 11:38 AM, Kees Cook 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;
> 

yeah this looks good it should at least hit stable

Acked-by: John Johansen <john.johansen@...onical.com>

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