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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 0011AC34056 for ; Wed, 19 Feb 2020 17:46:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CE0E3206DB for ; Wed, 19 Feb 2020 17:46:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Zg+vGQy4" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726725AbgBSRqx (ORCPT ); Wed, 19 Feb 2020 12:46:53 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:49768 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726634AbgBSRqx (ORCPT ); Wed, 19 Feb 2020 12:46:53 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=NKFJWW92BOtp7ehLpMCTv7FaSLRImYIzh5HecQGR8O8=; b=Zg+vGQy4LnfhuXpSONgFibaT7x 0q4ozltEg8I2EKUKp8gbbUbyE/k9kSOHbblYhVjFky/qCXedAMwVi/qXoDPo5WzwlMIVnZ+Gw8dQB FErjlQzpP+7aL90T05WzV3CNg0d4c+xaR4VhEJ76NQo0rDrAEVB82J5+p8yyVEVU8v+A3tEgekSPJ sz2DABsh4riQXC0PxzHr38jmk/s5KCnZ+5hJZxQRhGtSzrJW7n5EknpiOj7htc6/cy9vAPXdPm1EN K53kYIMFb61VL/Y6ysveuf5kx9IbCdjYwHs78MZGbEypuQ2u5cwZRXaT2NGkNvDktqBvi2mX9JyAl MIKs98+w==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1j4TQX-0008TS-S5; Wed, 19 Feb 2020 17:46:27 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id EB1CF300606; Wed, 19 Feb 2020 18:44:30 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 6070F285625FC; Wed, 19 Feb 2020 18:46:23 +0100 (CET) Date: Wed, 19 Feb 2020 18:46:23 +0100 From: Peter Zijlstra To: Borislav Petkov Cc: Andy Lutomirski , LKML , linux-arch , Steven Rostedt , Ingo Molnar , Joel Fernandes , Greg KH , gustavo@embeddedor.com, Thomas Gleixner , paulmck@kernel.org, Josh Triplett , Mathieu Desnoyers , Lai Jiangshan , Tony Luck , Frederic Weisbecker , Dan Carpenter , Masami Hiramatsu Subject: Re: [PATCH v3 02/22] x86,mce: Delete ist_begin_non_atomic() Message-ID: <20200219174623.GQ18400@hirez.programming.kicks-ass.net> References: <20200219144724.800607165@infradead.org> <20200219150744.488895196@infradead.org> <20200219171309.GC32346@zn.tnic> <20200219174223.GE30966@zn.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200219174223.GE30966@zn.tnic> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 19, 2020 at 06:42:23PM +0100, Borislav Petkov wrote: > On Wed, Feb 19, 2020 at 09:21:48AM -0800, Andy Lutomirski wrote: > > Unless there is a signal pending and the signal setup code is about to > > hit the same failed memory. I suppose we can just treat cases like > > this as "oh well, time to kill the whole system". > > > > But we should genuinely agree that we're okay with deferring this handling. > > Good catch! > > static void exit_to_usermode_loop(struct pt_regs *regs, u32 cached_flags) > { > > ... > > /* deal with pending signal delivery */ > if (cached_flags & _TIF_SIGPENDING) > do_signal(regs); > > if (cached_flags & _TIF_NOTIFY_RESUME) { > clear_thread_flag(TIF_NOTIFY_RESUME); > tracehook_notify_resume(regs); > rseq_handle_notify_resume(NULL, regs); > } > > > Err, can we make task_work run before we handle signals? Or there's a > reason it is run in this order? > > Comment over task_work_add() says: > > * This is like the signal handler which runs in kernel mode, but it doesn't > * try to wake up the @task. > > which sounds to me like this should really run before the signal > handlers... here goes... --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -155,16 +155,16 @@ static void exit_to_usermode_loop(struct if (cached_flags & _TIF_PATCH_PENDING) klp_update_patch_state(current); - /* deal with pending signal delivery */ - if (cached_flags & _TIF_SIGPENDING) - do_signal(regs); - if (cached_flags & _TIF_NOTIFY_RESUME) { clear_thread_flag(TIF_NOTIFY_RESUME); tracehook_notify_resume(regs); rseq_handle_notify_resume(NULL, regs); } + /* deal with pending signal delivery */ + if (cached_flags & _TIF_SIGPENDING) + do_signal(regs); + if (cached_flags & _TIF_USER_RETURN_NOTIFY) fire_user_return_notifiers();