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

From: Tycho Andersen <tycho.andersen@canonical.com>
To: Oleg Nesterov <oleg@redhat.com>,
	Kees Cook <keescook@chromium.org>,
	Andy Lutomirski <luto@amacapital.net>
Cc: linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
	Kees Cook <keescook@chromium.org>,
	Andy Lutomirski <luto@amacapital.net>,
	Will Drewry <wad@chromium.org>,
	Roland McGrath <roland@hack.frob.com>,
	Pavel Emelyanov <xemul@parallels.com>,
	"Serge E. Hallyn" <serge.hallyn@ubuntu.com>
Subject: Re: [PATCH v2] seccomp: add ptrace options for suspend/resume
Date: Tue, 9 Jun 2015 15:22:22 -0600	[thread overview]
Message-ID: <20150609212222.GE2045@hopstrocity> (raw)
In-Reply-To: <20150605211650.GA25718@redhat.com>

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?

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

Tycho