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=-7.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 494B2C4CEC7 for ; Sat, 14 Sep 2019 14:21:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1393320830 for ; Sat, 14 Sep 2019 14:21:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=efficios.com header.i=@efficios.com header.b="OrM9XPiI" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389386AbfINOVc (ORCPT ); Sat, 14 Sep 2019 10:21:32 -0400 Received: from mail.efficios.com ([167.114.142.138]:55114 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387786AbfINOVc (ORCPT ); Sat, 14 Sep 2019 10:21:32 -0400 Received: from localhost (ip6-localhost [IPv6:::1]) by mail.efficios.com (Postfix) with ESMTP id 5ADDB2B9B77; Sat, 14 Sep 2019 10:21:30 -0400 (EDT) Received: from mail.efficios.com ([IPv6:::1]) by localhost (mail02.efficios.com [IPv6:::1]) (amavisd-new, port 10032) with ESMTP id cVHedDvBx6U9; Sat, 14 Sep 2019 10:21:29 -0400 (EDT) Received: from localhost (ip6-localhost [IPv6:::1]) by mail.efficios.com (Postfix) with ESMTP id A942C2B9B73; Sat, 14 Sep 2019 10:21:29 -0400 (EDT) DKIM-Filter: OpenDKIM Filter v2.10.3 mail.efficios.com A942C2B9B73 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=efficios.com; s=default; t=1568470889; bh=M10BlrTXAj0G5y7uqqZ+tCLOJeUIc+aRdoN/am4d8Qs=; h=Date:From:To:Message-ID:MIME-Version; b=OrM9XPiIjv9+zo4an4UrG/+X9Ag8E8VsyGp9CSouhtbLgQHQW1q7RLxo2SzHPtUsB soLryC4pEL0QcFbWbUOekyDq1723FMIAjRpx3mHjDtlCYAo0BAlR7uNPHtaxST/BXc MbqYnsqaNRG0VOWwuAFAudaN6ntE/sNMq7rjrDe98AsXNaSwyiq/U24TRTww60ik2s vzdUrsQCuYuzvoF2S4LRxtgphBO34e1Vz3tW7L6tp8axudzkOnLZLDDRVWe/Bnw603 RxEbD/XB4OWilZUjwXNJ0mCQ443ugi0gnon4+XT/qiSTYIOVj4VDpd06+nxHDqAvVk 1ElusDH4V3glg== X-Virus-Scanned: amavisd-new at efficios.com Received: from mail.efficios.com ([IPv6:::1]) by localhost (mail02.efficios.com [IPv6:::1]) (amavisd-new, port 10026) with ESMTP id 4BJ5TKhxbPjp; Sat, 14 Sep 2019 10:21:29 -0400 (EDT) Received: from mail02.efficios.com (mail02.efficios.com [167.114.142.138]) by mail.efficios.com (Postfix) with ESMTP id 8FD772B9B69; Sat, 14 Sep 2019 10:21:29 -0400 (EDT) Date: Sat, 14 Sep 2019 10:21:29 -0400 (EDT) From: Mathieu Desnoyers To: Thomas Gleixner , Neel Natu Cc: linux-kernel , Peter Zijlstra , paulmck , Boqun Feng , "H. Peter Anvin" , Paul Turner , Dmitry Vyukov , linux-api , stable Message-ID: <819646407.3304.1568470889470.JavaMail.zimbra@efficios.com> In-Reply-To: <20190913151220.3105-2-mathieu.desnoyers@efficios.com> References: <20190913151220.3105-1-mathieu.desnoyers@efficios.com> <20190913151220.3105-2-mathieu.desnoyers@efficios.com> Subject: Re: [PATCH for 5.3 2/3] rseq: Fix: Unregister rseq for CLONE_SETTLS MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [167.114.142.138] X-Mailer: Zimbra 8.8.15_GA_3847 (ZimbraWebClient - FF69 (Linux)/8.8.15_GA_3847) Thread-Topic: rseq: Fix: Unregister rseq for CLONE_SETTLS Thread-Index: o9eZqvAOKmXphmxsJKc8X5whD/BREg== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There is an ongoing discussion on the choice of flag we want to care about here. Therefore, please don't pull this patch until we reach an agreement. Thanks, Mathieu ----- On Sep 13, 2019, at 11:12 AM, Mathieu Desnoyers mathieu.desnoyers@efficios.com wrote: > It has been reported by Google that rseq is not behaving properly > with respect to clone when CLONE_VM is used without CLONE_THREAD. > It keeps the prior thread's rseq TLS registered when the TLS of the > thread has moved, so the kernel deals with the wrong TLS. > > The approach of clearing the per task-struct rseq registration > on clone with CLONE_THREAD flag is incomplete. It does not cover > the use-case of clone with CLONE_VM set, but without CLONE_THREAD. > > Looking more closely at each of the clone flags: > > - CLONE_THREAD, > - CLONE_VM, > - CLONE_SETTLS. > > It appears that the flag we really want to track is CLONE_SETTLS, which > moves the location of the TLS for the child, making the rseq > registration point to the wrong TLS. > > Suggested-by: "H . Peter Anvin" > Signed-off-by: Mathieu Desnoyers > Cc: Thomas Gleixner > Cc: Peter Zijlstra (Intel) > Cc: "Paul E. McKenney" > Cc: Boqun Feng > Cc: "H . Peter Anvin" > Cc: Paul Turner > Cc: Dmitry Vyukov > Cc: linux-api@vger.kernel.org > Cc: > --- > include/linux/sched.h | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/include/linux/sched.h b/include/linux/sched.h > index 9f51932bd543..76bf55b5cccf 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -1919,11 +1919,11 @@ static inline void rseq_migrate(struct task_struct *t) > > /* > * If parent process has a registered restartable sequences area, the > - * child inherits. Only applies when forking a process, not a thread. > + * child inherits. Unregister rseq for a clone with CLONE_SETTLS set. > */ > static inline void rseq_fork(struct task_struct *t, unsigned long clone_flags) > { > - if (clone_flags & CLONE_THREAD) { > + if (clone_flags & CLONE_SETTLS) { > t->rseq = NULL; > t->rseq_sig = 0; > t->rseq_event_mask = 0; > -- > 2.17.1 -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com