linux-kernel - Re: [PATCH v8 3/9] seccomp: introduce writer locking

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Date:	Wed, 25 Jun 2014 20:29:07 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Kees Cook <keescook@...omium.org>
Cc:	linux-kernel@...r.kernel.org,
	Andy Lutomirski <luto@...capital.net>,
	"Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Daniel Borkmann <dborkman@...hat.com>,
	Will Drewry <wad@...omium.org>,
	Julien Tinnes <jln@...omium.org>,
	David Drysdale <drysdale@...gle.com>,
	linux-api@...r.kernel.org, x86@...nel.org,
	linux-arm-kernel@...ts.infradead.org, linux-mips@...ux-mips.org,
	linux-arch@...r.kernel.org, linux-security-module@...r.kernel.org
Subject: Re: [PATCH v8 3/9] seccomp: introduce writer locking

On 06/25, Oleg Nesterov wrote:
>
> On 06/24, Kees Cook wrote:
> >
> > +static void copy_seccomp(struct task_struct *p)
> > +{
> > +#ifdef CONFIG_SECCOMP
> > +	/*
> > +	 * Must be called with sighand->lock held, which is common to
> > +	 * all threads in the group. Regardless, nothing special is
> > +	 * needed for the child since it is not yet in the tasklist.
> > +	 */
> > +	BUG_ON(!spin_is_locked(&current->sighand->siglock));
> > +
> > +	get_seccomp_filter(current);
> > +	p->seccomp = current->seccomp;
> > +
> > +	if (p->seccomp.mode != SECCOMP_MODE_DISABLED)
> > +		set_tsk_thread_flag(p, TIF_SECCOMP);
> > +#endif
> > +}
>
> Wait. But what about no_new_privs? We should copy it as well...
>
> Perhaps this helper should be updated a bit and moved into seccomp.c so
> that seccomp_sync_threads() could use it too.

This way we can also unexport get_seccomp_filter().

Oleg.

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