linux-kernel - Re: PATCH? fix unshare(NEWPID) && vfork()

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Message-ID: <87siy4z1pf.fsf@xmission.com>
Date:	Tue, 20 Aug 2013 10:55:40 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Brad Spengler <spender@...ecurity.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Colin Walters <walters@...hat.com>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: PATCH? fix unshare(NEWPID) && vfork()

Oleg Nesterov <oleg@...hat.com> writes:

> On 08/19, Andy Lutomirski wrote:
>>
>> On Mon, Aug 19, 2013 at 11:33 AM, Oleg Nesterov <oleg@...hat.com> wrote:
>> >
>> > So do you think this change is fine or not (ignoring the fact it needs
>> > cleanups) ?
>>
>> I think that removing the CLONE_VM check is fine (although there are
>> some other ones that should probably be removed as well), but I'm not
>> sure if that check needs replacing with something else.
>
> OK, thanks... but I still can't understand.
>
> The patch I sent is equivalent to the new one below. I just tried to
> unify it with another check in do_fork().

The patch below also needs CLONE_SIGHAND.  You can't meaningfully share
signal handlers if you can't represent the pid in the siginfo.  pids and
signals are too interconnected.

Eric

> Oleg.
>
> --- x/kernel/fork.c
> +++ x/kernel/fork.c
> @@ -1176,7 +1176,7 @@ static struct task_struct *copy_process(
>  	 * If the new process will be in a different pid namespace
>  	 * don't allow the creation of threads.
>  	 */
> -	if ((clone_flags & (CLONE_VM|CLONE_NEWPID)) &&
> +	if ((clone_flags & (CLONE_THREAD | CLONE_PARENT | CLONE_NEWPID)) &&
>  	    (task_active_pid_ns(current) != current->nsproxy->pid_ns))
>  		return ERR_PTR(-EINVAL);
>  
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