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

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Date:	Thu, 22 Aug 2013 18:47:03 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.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@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: PATCH? fix unshare(NEWPID) && vfork()

On 08/21, Oleg Nesterov wrote:
>
> Still. Can't we make a single check? Like the initial patch I sent, but
> this one moves the check into copy_process() and checks CLONE_* first.
> Looks a bit simpler. And more understandable to me but this is subjective.

Seriously. CLONE_NEWPID and task_active_pid_ns() != nsproxy->pid_ns are
the same thing in this respect. Let me send the patches for review, I
decided to split this change.

> --- x/kernel/fork.c
> +++ x/kernel/fork.c
> @@ -1173,12 +1173,13 @@ static struct task_struct *copy_process(
>  		return ERR_PTR(-EINVAL);
>  
>  	/*
> -	 * If the new process will be in a different pid namespace
> -	 * don't allow the creation of threads.
> +	 * --------------  COMMENT -----------------
>  	 */
> -	if ((clone_flags & (CLONE_VM|CLONE_NEWPID)) &&
> -	    (task_active_pid_ns(current) != current->nsproxy->pid_ns))
> -		return ERR_PTR(-EINVAL);
> +	if (clone_flags & (CLONE_SIGHAND | CLONE_PARENT)) {
> +		if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
> +		    (task_active_pid_ns(current) != current->nsproxy->pid_ns))
> +			return -EINVAL;
                                ^^^^^^

should be ERR_PTR(-EINVAL)

Oleg.

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