From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Tue, 24 Jun 2014 19:54:18 +0200 (CEST) Received: from mx1.redhat.com ([209.132.183.28]:2902 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by eddie.linux-mips.org with ESMTP id S6816503AbaFXRyQrS3-Y (ORCPT ); Tue, 24 Jun 2014 19:54:16 +0200 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id s5OH95Fi020583 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 24 Jun 2014 13:09:06 -0400 Received: from tranklukator.brq.redhat.com (dhcp-1-125.brq.redhat.com [10.34.1.125]) by int-mx09.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with SMTP id s5OH91xH001734; Tue, 24 Jun 2014 13:09:02 -0400 Received: by tranklukator.brq.redhat.com (nbSMTP-1.00) for uid 500 oleg@redhat.com; Tue, 24 Jun 2014 19:08:04 +0200 (CEST) Date: Tue, 24 Jun 2014 19:08:00 +0200 From: Oleg Nesterov To: Kees Cook Cc: linux-kernel@vger.kernel.org, Andy Lutomirski , Alexei Starovoitov , "Michael Kerrisk (man-pages)" , Andrew Morton , Daniel Borkmann , Will Drewry , Julien Tinnes , David Drysdale , linux-api@vger.kernel.org, x86@kernel.org, linux-arm-kernel@lists.infradead.org, linux-mips@linux-mips.org, linux-arch@vger.kernel.org, linux-security-module@vger.kernel.org Subject: Re: [PATCH v7 7/9] seccomp: implement SECCOMP_FILTER_FLAG_TSYNC Message-ID: <20140624170800.GA30480@redhat.com> References: <1403560693-21809-1-git-send-email-keescook@chromium.org> <1403560693-21809-8-git-send-email-keescook@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1403560693-21809-8-git-send-email-keescook@chromium.org> User-Agent: Mutt/1.5.18 (2008-05-17) X-Scanned-By: MIMEDefang 2.68 on 10.5.11.22 Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 40754 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: oleg@redhat.com Precedence: bulk List-help: List-unsubscribe: List-software: Ecartis version 1.0.0 List-Id: linux-mips X-List-ID: linux-mips List-subscribe: List-owner: List-post: List-archive: X-list: linux-mips On 06/23, Kees Cook wrote: > > +static pid_t seccomp_can_sync_threads(void) > +{ > + struct task_struct *thread, *caller; > + > + BUG_ON(write_can_lock(&tasklist_lock)); > + BUG_ON(!spin_is_locked(¤t->sighand->siglock)); > + > + if (current->seccomp.mode != SECCOMP_MODE_FILTER) > + return -EACCES; > + > + /* Validate all threads being eligible for synchronization. */ > + thread = caller = current; > + for_each_thread(caller, thread) { You only need to initialize "caller" for for_each_thread(). Same for seccomp_sync_threads(). > @@ -586,6 +701,17 @@ static long seccomp_set_mode_filter(unsigned int flags, > if (IS_ERR(prepared)) > return PTR_ERR(prepared); > > + /* > + * If we're doing thread sync, we must hold tasklist_lock > + * to make sure seccomp filter changes are stable on threads > + * entering or leaving the task list. And we must take it > + * before the sighand lock to avoid deadlocking. > + */ > + if (flags & SECCOMP_FILTER_FLAG_TSYNC) > + write_lock_irqsave(&tasklist_lock, taskflags); > + else > + __acquire(&tasklist_lock); /* keep sparse happy */ > + Why? ->siglock should be enough, it seems. It obviously does not protect the global process list, but *sync_threads() only care about current's thread group list, no? Oleg.