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

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Date:	Tue, 9 Jun 2015 15:22:22 -0600
From:	Tycho Andersen <tycho.andersen@...onical.com>
To:	Oleg Nesterov <oleg@...hat.com>, Kees Cook <keescook@...omium.org>,
	Andy Lutomirski <luto@...capital.net>
Cc:	linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
	Kees Cook <keescook@...omium.org>,
	Andy Lutomirski <luto@...capital.net>,
	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

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
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