linux-kernel - Re: [PATCH v2] seccomp: add ptrace options for suspend/resume

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Date:	Tue, 9 Jun 2015 14:45:49 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Tycho Andersen <tycho.andersen@...onical.com>
Cc:	Oleg Nesterov <oleg@...hat.com>,
	Andy Lutomirski <luto@...capital.net>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux API <linux-api@...r.kernel.org>,
	Will Drewry <wad@...omium.org>,
	Roland McGrath <roland@...k.frob.com>,
	Pavel Emelyanov <xemul@...allels.com>,
	"Serge E. Hallyn" <serge.hallyn@...ntu.com>
Subject: Re: [PATCH v2] seccomp: add ptrace options for suspend/resume

On Tue, Jun 9, 2015 at 2:22 PM, Tycho Andersen
<tycho.andersen@...onical.com> wrote:
> Hi Kees, Andy,
>
> On Fri, Jun 05, 2015 at 11:16:50PM +0200, Oleg Nesterov wrote:
>> Hi Tycho,
>>
>> On 06/04, Tycho Andersen wrote:
>> > > > +#ifdef CONFIG_CHECKPOINT_RESTORE
>> > > > +bool may_suspend_seccomp(void)
>> > > > +{
>> > > > +       if (!capable(CAP_SYS_ADMIN))
>> > > > +               return false;
>> > > > +
>> > > > +       if (current->seccomp.mode != SECCOMP_MODE_DISABLED)
>> > > > +               return false;
>> > >
>> > > Heh. OK, I won't argue with the new check too ;)
>> >
>> > Actually now that I think about it I agree with you, these checks
>> > don't seem necessary. Even inside a user namespace, if you can ptrace
>> > a process you can make it do whatever you want irrespective of
>> > seccomp, as long as it has the necessary capabilities. Once the
>> > seccomp checks are run after ptrace, they'll be enforced so you
>> > couldn't have it call whatever you want in the first place.
>>
>> Good ;)
>>
>> > Still, perhaps I'm missing something...
>>
>> Kees, Andy?
>
> Any thoughts on removing may_suspend_seccomp() all together?

As in, just open-code the check? That would be fine by me.

> I sent v3 with this still in it, but I can send v4 without it if we
> are all in agreement.

-Kees

-- 
Kees Cook
Chrome OS Security
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