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=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,T_DKIMWL_WL_HIGH 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 4B39FC433F5 for ; Tue, 28 Aug 2018 23:32:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E8BFF2088E for ; Tue, 28 Aug 2018 23:32:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="0ebp22GA" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E8BFF2088E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727535AbeH2D01 (ORCPT ); Tue, 28 Aug 2018 23:26:27 -0400 Received: from mail.kernel.org ([198.145.29.99]:54170 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727104AbeH2D01 (ORCPT ); Tue, 28 Aug 2018 23:26:27 -0400 Received: from devbox (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (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 CE9E52087D; Tue, 28 Aug 2018 23:32:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1535499149; bh=UmL00Yaksy0hl3YcTc1u6uHjx3BKzGNCkF9oYb2qTP4=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=0ebp22GABwKs8oiiujqXRy0aA2rFh9cVP2ZbGmhHRF+cJ7Gp2MVqISPZDmALjopBH ZVJE5Dlz7N2m5LfdiIkFwm9QHA9yz0RfViCJKtrpMn513GsKkmymgd/9PANXCEUki+ +kotR/dPM/GitAB1YZJGBqzkvQeygoe9QRgo7U48= Date: Wed, 29 Aug 2018 08:32:24 +0900 From: Masami Hiramatsu To: Jann Horn Cc: Kees Cook , Thomas Gleixner , Ingo Molnar , x86@kernel.org, Andy Lutomirski , kernel-hardening@lists.openwall.com, linux-kernel@vger.kernel.org, dvyukov@google.com, Masami Hiramatsu , "Naveen N. Rao" , Anil S Keshavamurthy , "David S. Miller" , Alexander Viro , linux-fsdevel@vger.kernel.org, Borislav Petkov Subject: Re: [PATCH v3 1/7] x86: refactor kprobes_fault() like kprobe_exceptions_notify() Message-Id: <20180829083224.6b01b8f04872855d90c4786a@kernel.org> In-Reply-To: <20180828201421.157735-2-jannh@google.com> References: <20180828201421.157735-1-jannh@google.com> <20180828201421.157735-2-jannh@google.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 28 Aug 2018 22:14:15 +0200 Jann Horn wrote: > This is an extension of commit b506a9d08bae ("x86: code clarification patch > to Kprobes arch code"). As that commit explains, even though > kprobe_running() can't be called with preemption enabled, you don't have to > disable preemption - if preemption is on, you can't be in a kprobe. > > Also, use X86_TRAP_PF instead of 14. > > Signed-off-by: Jann Horn > --- > v3: > - avoid unnecessary branch on return value and split up the checks > (Borislav Petkov) > > arch/x86/mm/fault.c | 24 +++++++++++++----------- > 1 file changed, 13 insertions(+), 11 deletions(-) > > diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c > index b9123c497e0a..bcdaae1d5bf5 100644 > --- a/arch/x86/mm/fault.c > +++ b/arch/x86/mm/fault.c > @@ -44,17 +44,19 @@ kmmio_fault(struct pt_regs *regs, unsigned long addr) > > static nokprobe_inline int kprobes_fault(struct pt_regs *regs) > { > - int ret = 0; > - > - /* kprobe_running() needs smp_processor_id() */ > - if (kprobes_built_in() && !user_mode(regs)) { > - preempt_disable(); > - if (kprobe_running() && kprobe_fault_handler(regs, 14)) > - ret = 1; > - preempt_enable(); > - } > - > - return ret; > + if (!kprobes_built_in()) > + return 0; > + if (user_mode(regs)) > + return 0; > + /* > + * To be potentially processing a kprobe fault and to be allowed to call > + * kprobe_running(), we have to be non-preemptible. Good catch! Acked-by: Masami Hiramatsu Thanks! > + */ > + if (preemptible()) > + return 0; > + if (!kprobe_running()) > + return 0; > + return kprobe_fault_handler(regs, X86_TRAP_PF); > } > > /* > -- > 2.19.0.rc0.228.g281dcd1b4d0-goog > -- Masami Hiramatsu