From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Tue, 24 Jun 2014 20:39:14 +0200 (CEST) Received: from mx1.redhat.com ([209.132.183.28]:30993 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by eddie.linux-mips.org with ESMTP id S6854779AbaFXSjM3O1Vt (ORCPT ); Tue, 24 Jun 2014 20:39:12 +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 s5OIcsQH025577 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 24 Jun 2014 14:38:55 -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 s5OIcoS3022502; Tue, 24 Jun 2014 14:38:51 -0400 Received: by tranklukator.brq.redhat.com (nbSMTP-1.00) for uid 500 oleg@redhat.com; Tue, 24 Jun 2014 20:37:53 +0200 (CEST) Date: Tue, 24 Jun 2014 20:37:49 +0200 From: Oleg Nesterov To: Kees Cook Cc: LKML , Andy Lutomirski , Alexei Starovoitov , "Michael Kerrisk (man-pages)" , Andrew Morton , Daniel Borkmann , Will Drewry , Julien Tinnes , David Drysdale , Linux API , "x86@kernel.org" , "linux-arm-kernel@lists.infradead.org" , linux-mips@linux-mips.org, linux-arch , linux-security-module Subject: Re: [PATCH v7 7/9] seccomp: implement SECCOMP_FILTER_FLAG_TSYNC Message-ID: <20140624183749.GC1258@redhat.com> References: <1403560693-21809-1-git-send-email-keescook@chromium.org> <1403560693-21809-8-git-send-email-keescook@chromium.org> <20140624172753.GA31435@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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: 40761 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 06/24, Kees Cook wrote: > > On Tue, Jun 24, 2014 at 10:27 AM, Oleg Nesterov wrote: > > 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) { > >> + pid_t failed; > >> + > >> + if (thread->seccomp.mode == SECCOMP_MODE_DISABLED || > >> + (thread->seccomp.mode == SECCOMP_MODE_FILTER && > >> + is_ancestor(thread->seccomp.filter, > >> + caller->seccomp.filter))) > >> + continue; > >> + > >> + /* Return the first thread that cannot be synchronized. */ > >> + failed = task_pid_vnr(thread); > >> + /* If the pid cannot be resolved, then return -ESRCH */ > >> + if (failed == 0) > >> + failed = -ESRCH; > > > > forgot to mention, task_pid_vnr() can't fail. sighand->siglock is held, > > for_each_thread() can't see a thread which has passed unhash_process(). > > Certainly good to know, but I'd be much more comfortable leaving this > check as-is. Having "failed" return with "0" would be very very bad > (userspace would think the filter had been successfully applied, etc). > I'd rather stay highly defensive here. OK, agreed. Although in this case I'd suggest if (WARN_ON(failed == 0)) failed = -ESRCH; but I won't insist. Oleg. From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx1.redhat.com ([209.132.183.28]:30993 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by eddie.linux-mips.org with ESMTP id S6854779AbaFXSjM3O1Vt (ORCPT ); Tue, 24 Jun 2014 20:39:12 +0200 Date: Tue, 24 Jun 2014 20:37:49 +0200 From: Oleg Nesterov Subject: Re: [PATCH v7 7/9] seccomp: implement SECCOMP_FILTER_FLAG_TSYNC Message-ID: <20140624183749.GC1258@redhat.com> References: <1403560693-21809-1-git-send-email-keescook@chromium.org> <1403560693-21809-8-git-send-email-keescook@chromium.org> <20140624172753.GA31435@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Return-Path: Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org List-help: List-unsubscribe: List-software: Ecartis version 1.0.0 List-subscribe: List-owner: List-post: List-archive: To: Kees Cook Cc: LKML , Andy Lutomirski , Alexei Starovoitov , "Michael Kerrisk (man-pages)" , Andrew Morton , Daniel Borkmann , Will Drewry , Julien Tinnes , David Drysdale , Linux API , "x86@kernel.org" , "linux-arm-kernel@lists.infradead.org" , linux-mips@linux-mips.org, linux-arch , linux-security-module Message-ID: <20140624183749.dim65lfxccdqZCHamJtNQA-dubHy9O0kIoV1ZyAvReE@z> On 06/24, Kees Cook wrote: > > On Tue, Jun 24, 2014 at 10:27 AM, Oleg Nesterov wrote: > > 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) { > >> + pid_t failed; > >> + > >> + if (thread->seccomp.mode == SECCOMP_MODE_DISABLED || > >> + (thread->seccomp.mode == SECCOMP_MODE_FILTER && > >> + is_ancestor(thread->seccomp.filter, > >> + caller->seccomp.filter))) > >> + continue; > >> + > >> + /* Return the first thread that cannot be synchronized. */ > >> + failed = task_pid_vnr(thread); > >> + /* If the pid cannot be resolved, then return -ESRCH */ > >> + if (failed == 0) > >> + failed = -ESRCH; > > > > forgot to mention, task_pid_vnr() can't fail. sighand->siglock is held, > > for_each_thread() can't see a thread which has passed unhash_process(). > > Certainly good to know, but I'd be much more comfortable leaving this > check as-is. Having "failed" return with "0" would be very very bad > (userspace would think the filter had been successfully applied, etc). > I'd rather stay highly defensive here. OK, agreed. Although in this case I'd suggest if (WARN_ON(failed == 0)) failed = -ESRCH; but I won't insist. Oleg.