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=-12.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,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 32536C43441 for ; Fri, 23 Nov 2018 07:35:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0229D206B2 for ; Fri, 23 Nov 2018 07:35:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0229D206B2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=zytor.com 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 S2502343AbeKWSSb (ORCPT ); Fri, 23 Nov 2018 13:18:31 -0500 Received: from terminus.zytor.com ([198.137.202.136]:45337 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2502329AbeKWSSb (ORCPT ); Fri, 23 Nov 2018 13:18:31 -0500 Received: from terminus.zytor.com (localhost [127.0.0.1]) by terminus.zytor.com (8.15.2/8.15.2) with ESMTPS id wAN7Xp2P4112169 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Thu, 22 Nov 2018 23:33:51 -0800 Received: (from tipbot@localhost) by terminus.zytor.com (8.15.2/8.15.2/Submit) id wAN7Xpgj4112166; Thu, 22 Nov 2018 23:33:51 -0800 Date: Thu, 22 Nov 2018 23:33:51 -0800 X-Authentication-Warning: terminus.zytor.com: tipbot set sender to tipbot@zytor.com using -f From: tip-bot for Andrea Parri Message-ID: Cc: eranian@google.com, tglx@linutronix.de, mingo@kernel.org, akpm@linux-foundation.org, hpa@zytor.com, torvalds@linux-foundation.org, namhyung@kernel.org, jolsa@redhat.com, andrea.parri@amarulasolutions.com, paulmck@linux.vnet.ibm.com, acme@redhat.com, oleg@redhat.com, vincent.weaver@maine.edu, alexander.shishkin@linux.intel.com, peterz@infradead.org, linux-kernel@vger.kernel.org Reply-To: linux-kernel@vger.kernel.org, alexander.shishkin@linux.intel.com, peterz@infradead.org, vincent.weaver@maine.edu, acme@redhat.com, oleg@redhat.com, paulmck@linux.vnet.ibm.com, andrea.parri@amarulasolutions.com, jolsa@redhat.com, torvalds@linux-foundation.org, namhyung@kernel.org, hpa@zytor.com, akpm@linux-foundation.org, mingo@kernel.org, eranian@google.com, tglx@linutronix.de In-Reply-To: <20181122161031.15179-1-andrea.parri@amarulasolutions.com> References: <20181122161031.15179-1-andrea.parri@amarulasolutions.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:perf/urgent] uprobes: Fix handle_swbp() vs. unregister() + register() race once more Git-Commit-ID: 09d3f015d1e1b4fee7e9bbdcf54201d239393391 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 09d3f015d1e1b4fee7e9bbdcf54201d239393391 Gitweb: https://git.kernel.org/tip/09d3f015d1e1b4fee7e9bbdcf54201d239393391 Author: Andrea Parri AuthorDate: Thu, 22 Nov 2018 17:10:31 +0100 Committer: Ingo Molnar CommitDate: Fri, 23 Nov 2018 08:31:19 +0100 uprobes: Fix handle_swbp() vs. unregister() + register() race once more Commit: 142b18ddc8143 ("uprobes: Fix handle_swbp() vs unregister() + register() race") added the UPROBE_COPY_INSN flag, and corresponding smp_wmb() and smp_rmb() memory barriers, to ensure that handle_swbp() uses fully-initialized uprobes only. However, the smp_rmb() is mis-placed: this barrier should be placed after handle_swbp() has tested for the flag, thus guaranteeing that (program-order) subsequent loads from the uprobe can see the initial stores performed by prepare_uprobe(). Move the smp_rmb() accordingly. Also amend the comments associated to the two memory barriers to indicate their actual locations. Signed-off-by: Andrea Parri Acked-by: Oleg Nesterov Cc: Alexander Shishkin Cc: Andrew Morton Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Linus Torvalds Cc: Namhyung Kim Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Thomas Gleixner Cc: Vince Weaver Cc: stable@kernel.org Fixes: 142b18ddc8143 ("uprobes: Fix handle_swbp() vs unregister() + register() race") Link: http://lkml.kernel.org/r/20181122161031.15179-1-andrea.parri@amarulasolutions.com Signed-off-by: Ingo Molnar --- kernel/events/uprobes.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 96d4bee83489..322e97bbb437 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -829,7 +829,7 @@ static int prepare_uprobe(struct uprobe *uprobe, struct file *file, BUG_ON((uprobe->offset & ~PAGE_MASK) + UPROBE_SWBP_INSN_SIZE > PAGE_SIZE); - smp_wmb(); /* pairs with rmb() in find_active_uprobe() */ + smp_wmb(); /* pairs with the smp_rmb() in handle_swbp() */ set_bit(UPROBE_COPY_INSN, &uprobe->flags); out: @@ -2178,10 +2178,18 @@ static void handle_swbp(struct pt_regs *regs) * After we hit the bp, _unregister + _register can install the * new and not-yet-analyzed uprobe at the same address, restart. */ - smp_rmb(); /* pairs with wmb() in install_breakpoint() */ if (unlikely(!test_bit(UPROBE_COPY_INSN, &uprobe->flags))) goto out; + /* + * Pairs with the smp_wmb() in prepare_uprobe(). + * + * Guarantees that if we see the UPROBE_COPY_INSN bit set, then + * we must also see the stores to &uprobe->arch performed by the + * prepare_uprobe() call. + */ + smp_rmb(); + /* Tracing handlers use ->utask to communicate with fetch methods */ if (!get_utask()) goto out;