linux-kernel - Re: [PATCH] proc: don't show nonexistent capabilities (v2)

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Date:	Sun, 7 Oct 2012 09:58:26 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Andrew Vagin <avagin@...nvz.org>
Cc:	linux-kernel@...r.kernel.org,
	"Andrew G. Morgan" <morgan@...nel.org>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	Pavel Emelyanov <xemul@...allels.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH] proc: don't show nonexistent capabilities (v2)

On Sun, Oct 7, 2012 at 2:56 AM, Andrew Vagin <avagin@...nvz.org> wrote:
> Without this patch it is really hard to interpret a bounding set,
> if CAP_LAST_CAP is unknown for a current kernel.
>
> Non-existant capabilities can not be deleted from a bounding set
> with help of prctl.
>
> E.g.: Here are two examples without/with this patch.
> CapBnd: ffffffe0fdecffff
> CapBnd: 00000000fdecffff
>
> I suggest to hide non-existent capabilities. Here is two reasons.
> * It's logically and easier for using.
> * It helps to checkpoint-restore capabilities of tasks, because tasks
> can be restored on another kernel, where CAP_LAST_CAP is bigger.
>
> v2: Non-existent capabilities can not be removed from creds, because
>     in this case user cannot set all=eip. This patch cleans up non-existent
>     capabilities from content of /proc/pid/status
>
> Cc: Andrew G. Morgan <morgan@...nel.org>
> Cc: Serge Hallyn <serge.hallyn@...onical.com>
> Cc: Pavel Emelyanov <xemul@...allels.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> Signed-off-by: Andrew Vagin <avagin@...nvz.org>

Seems sensible to me.

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

-Kees

-- 
Kees Cook
Chrome OS Security
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