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=-10.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 D5FF8C04EBF for ; Wed, 5 Dec 2018 09:44:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9BB9320878 for ; Wed, 5 Dec 2018 09:44:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="oDc4QaAn" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9BB9320878 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 S1729296AbeLEJo4 (ORCPT ); Wed, 5 Dec 2018 04:44:56 -0500 Received: from mail.kernel.org ([198.145.29.99]:49624 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728059AbeLEJoy (ORCPT ); Wed, 5 Dec 2018 04:44:54 -0500 Received: from sasha-vm.mshome.net (unknown [213.57.143.11]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 87367208E7; Wed, 5 Dec 2018 09:44:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1544003093; bh=k3m4FbzSpMwzlFQPy+D37AqWNc1svZXeT65y/k+HLS4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=oDc4QaAndugsXjYAetmoxy/biqb5R1cv1qYc4BFeKfvP5rgaeevt93tYSHpCSlWBN 2+Mamt0BYABkGN+CapGrzFTX9FBPnGKICLMwQBPnvHgaVpHU1+/Cv7aJENf1vzWhNB xb4E201yGBzsVAiwPLf8ZLSIxf2RyadJp7TKkexQ= From: Sasha Levin To: stable@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Andrea Parri , Alexander Shishkin , Andrew Morton , Arnaldo Carvalho de Melo , Jiri Olsa , Linus Torvalds , Namhyung Kim , "Paul E . McKenney" , Peter Zijlstra , Stephane Eranian , Thomas Gleixner , Vince Weaver , stable@kernel.org, Ingo Molnar , Sasha Levin Subject: [PATCH AUTOSEL 4.14 27/69] uprobes: Fix handle_swbp() vs. unregister() + register() race once more Date: Wed, 5 Dec 2018 04:42:05 -0500 Message-Id: <20181205094247.6556-27-sashal@kernel.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20181205094247.6556-1-sashal@kernel.org> References: <20181205094247.6556-1-sashal@kernel.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Andrea Parri [ Upstream commit 09d3f015d1e1b4fee7e9bbdcf54201d239393391 ] 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 Signed-off-by: Sasha Levin --- 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 267f6ef91d97..01941cffa9c2 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -616,7 +616,7 @@ 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: @@ -1910,10 +1910,18 @@ 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; -- 2.17.1