From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_2 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 28C2BC433DF for ; Sat, 27 Jun 2020 22:12:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 080C1207E8 for ; Sat, 27 Jun 2020 22:12:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726601AbgF0WMS convert rfc822-to-8bit (ORCPT ); Sat, 27 Jun 2020 18:12:18 -0400 Received: from mail.kernel.org ([198.145.29.99]:37584 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725916AbgF0WMS (ORCPT ); Sat, 27 Jun 2020 18:12:18 -0400 Received: from oasis.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 3040520706; Sat, 27 Jun 2020 22:12:16 +0000 (UTC) Date: Sat, 27 Jun 2020 18:12:14 -0400 From: Steven Rostedt To: Mike Rapoport Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Ben Segall , Mel Gorman , Mike Rapoport , Kees Cook Subject: Re: [PATCH] sched: fix build with GCC_PLUGIN_RANDSTRUCT Message-ID: <20200627181214.3a4d4a42@oasis.local.home> In-Reply-To: <20200620104136.12195-1-rppt@kernel.org> References: <20200620104136.12195-1-rppt@kernel.org> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 20 Jun 2020 13:41:36 +0300 Mike Rapoport wrote: > From: Mike Rapoport > > Since the commit a148866489fb ("sched: Replace rq::wake_list") > task_struct and CSD_TYPE_TTWU objects can be on the same queue and this > requires that have "layout similar enough". > > This assumption is broken when CONFIG_GCC_PLUGIN_RANDSTRUCT is enabled: You forgot to Cc Kees, who's the one that is probably the most concerned about randomizing structures! > > CHK include/generated/compile.h > CC kernel/smp.o > In file included from arch/x86/include/asm/atomic.h:5, > from include/linux/atomic.h:7, > from include/linux/llist.h:51, > from include/linux/irq_work.h:5, > from kernel/smp.c:10: > kernel/smp.c: In function ‘smp_init’: > include/linux/compiler.h:392:38: error: call to ‘__compiletime_assert_157’ declared with attribute error: BUILD_BUG_ON failed: offsetof(struct task_struct, wake_entry_type) - offsetof(struct task_struct, wake_entry) != offsetof(struct __call_single_data, flags) - offsetof(struct __call_single_data, llist) > 392 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) > | ^ > include/linux/compiler.h:373:4: note: in definition of macro ‘__compiletime_assert’ > 373 | prefix ## suffix(); \ > | ^~~~~~ > include/linux/compiler.h:392:2: note: in expansion of macro ‘_compiletime_assert’ > 392 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) > | ^~~~~~~~~~~~~~~~~~~ > include/linux/build_bug.h:39:37: note: in expansion of macro ‘compiletime_assert’ > 39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg) > | ^~~~~~~~~~~~~~~~~~ > include/linux/build_bug.h:50:2: note: in expansion of macro ‘BUILD_BUG_ON_MSG’ > 50 | BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition) > | ^~~~~~~~~~~~~~~~ > kernel/smp.c:687:2: note: in expansion of macro ‘BUILD_BUG_ON’ > 687 | BUILD_BUG_ON(offsetof(struct task_struct, wake_entry_type) - offsetof(struct task_struct, wake_entry) != > | ^~~~~~~~~~~~ > make[2]: *** [scripts/Makefile.build:280: kernel/smp.o] Error 1 > make[1]: *** [Makefile:1764: kernel] Error 2 > make[1]: *** Waiting for unfinished jobs.... > make[1]: Leaving directory '/home/mike/build/kernel' > make: *** [Makefile:185: __sub-make] Error 2 Seems the dependency is that the offsets between wake_entry and wake_entry_type doesn't change. > > Move 'wake_entry' and 'wake_entry_type' fiels of task_struct out of > the randomized fields to keep their layout intact. > > Signed-off-by: Mike Rapoport > --- > include/linux/sched.h | 11 +++++++++-- > 1 file changed, 9 insertions(+), 2 deletions(-) > > diff --git a/include/linux/sched.h b/include/linux/sched.h > index b62e6aaf28f0..c885573669ac 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -641,6 +641,15 @@ struct task_struct { > /* -1 unrunnable, 0 runnable, >0 stopped: */ > volatile long state; > > + /* > + * The layout of these fields must match the layout > CSD_TYPE_TTWU > + * so they can be on the same the @call_single_queue > + */ > +#ifdef CONFIG_SMP > + struct llist_node wake_entry; > + unsigned int wake_entry_type; > +#endif > + > /* > * This begins the randomizable portion of task_struct. Only > * scheduling-critical items should be added above here. > @@ -654,8 +663,6 @@ struct task_struct { > unsigned int ptrace; > > #ifdef CONFIG_SMP > - struct llist_node wake_entry; > - unsigned int wake_entry_type; What about instead just create an anonymous structure of the two. That way they can still be randomized within the task struct and not be a target of attacks? struct { struct llist_node wake_entry; unsigned int wake_entry_type; }; Would that work? -- Steve > int on_cpu; > #ifdef CONFIG_THREAD_INFO_IN_TASK > /* Current CPU: */