From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932084Ab3HWSE6 (ORCPT ); Fri, 23 Aug 2013 14:04:58 -0400 Received: from mx1.redhat.com ([209.132.183.28]:29173 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755864Ab3HWSE5 (ORCPT ); Fri, 23 Aug 2013 14:04:57 -0400 Date: Fri, 23 Aug 2013 19:59:03 +0200 From: Oleg Nesterov To: Andrew Morton , "Eric W. Biederman" Cc: Andy Lutomirski , Brad Spengler , Colin Walters , Linus Torvalds , Pavel Emelyanov , linux-kernel@vger.kernel.org Subject: [PATCH v2 1/3] pidns: fix vfork() after unshare(CLONE_NEWPID) Message-ID: <20130823175903.GA30219@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130823175846.GA30201@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 8382fcac "pidns: Outlaw thread creation after unshare(CLONE_NEWPID)" nacks CLONE_VM if the forking process unshared pid_ns, this obviously breaks vfork: int main(void) { assert(unshare(CLONE_NEWUSER | CLONE_NEWPID) == 0); assert(vfork() >= 0); _exit(0); return 0; } fails without this patch. Change this check to use CLONE_SIGHAND instead. This also forbids CLONE_THREAD automatically, and this is what the comment implies. We could probably even drop CLONE_SIGHAND and use CLONE_THREAD, but it would be safer to not do this. The current check denies CLONE_SIGHAND implicitely and there is no reason to change this. Reported-by: Colin Walters Signed-off-by: Oleg Nesterov Acked-by: Andy Lutomirski --- kernel/fork.c | 7 ++++--- 1 files changed, 4 insertions(+), 3 deletions(-) diff --git a/kernel/fork.c b/kernel/fork.c index e23bb19..29c9f6b 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1173,10 +1173,11 @@ static struct task_struct *copy_process(unsigned long clone_flags, return ERR_PTR(-EINVAL); /* - * If the new process will be in a different pid namespace - * don't allow the creation of threads. + * If the new process will be in a different pid namespace don't + * allow it to share a thread group or signal handlers with the + * forking task. */ - if ((clone_flags & (CLONE_VM|CLONE_NEWPID)) && + if ((clone_flags & (CLONE_SIGHAND | CLONE_NEWPID)) && (task_active_pid_ns(current) != current->nsproxy->pid_ns)) return ERR_PTR(-EINVAL); -- 1.5.5.1