linux-kernel - Re: [PATCH] prctl: Use CAP_SYS_RESOUCE for PR_SET

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Message-ID: <CAGXu5jL2QWWdnA-T3RQDWCaOuCcW8dvBXfGFBb6Oe9C1zT3oJw@mail.gmail.com>
Date:	Wed, 7 Mar 2012 09:03:27 -0800
From:	Kees Cook <keescook@...omium.org>
To:	Cyrill Gorcunov <gorcunov@...nvz.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	Pavel Emelyanov <xemul@...allels.com>,
	Tejun Heo <tj@...nel.org>, Oleg Nesterov <oleg@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Subject: Re: [PATCH] prctl: Use CAP_SYS_RESOUCE for PR_SET_MM option

On Wed, Mar 7, 2012 at 4:52 AM, Cyrill Gorcunov <gorcunov@...nvz.org> wrote:
> CAP_SYS_ADMIN is already overloaded left and right,
> so to have more finegrained access control use
> CAP_SYS_RESOUCE here.
>
> The CAP_SYS_RESOUCE is chosen because this prctl
> option allows a current process to adjust some
> fields of memory map descriptor which rather
> represent what the process owns: pointers to
> code, data, stack segments, command line,
> auxilary vector data and etc.
>
> Suggested-by: Michael Kerrisk <mtk.manpages@...il.com>
> CC: Andrew Morton <akpm@...ux-foundation.org>
> CC: Pavel Emelyanov <xemul@...allels.com>
> CC: Tejun Heo <tj@...nel.org>
> CC: Oleg Nesterov <oleg@...hat.com>
> CC: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> CC: Kees Cook <keescook@...omium.org>
> Signed-off-by: Cyrill Gorcunov <gorcunov@...nvz.org>
> ---
>  kernel/sys.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> Index: linux-2.6.git/kernel/sys.c
> ===================================================================
> --- linux-2.6.git.orig/kernel/sys.c
> +++ linux-2.6.git/kernel/sys.c
> @@ -1712,7 +1712,7 @@ static int prctl_set_mm(int opt, unsigne
>        if (arg5 || (arg4 && opt != PR_SET_MM_AUXV))
>                return -EINVAL;
>
> -       if (!capable(CAP_SYS_ADMIN))
> +       if (!capable(CAP_SYS_RESOURCE))
>                return -EPERM;
>
>        if (addr >= TASK_SIZE)

Yeah, getting away from CAP_SYS_ADMIN is a good idea.

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

-- 
Kees Cook
ChromeOS Security
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