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=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 6AE08C433DB for ; Tue, 23 Feb 2021 14:36:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3128364DD3 for ; Tue, 23 Feb 2021 14:36:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233083AbhBWOgA (ORCPT ); Tue, 23 Feb 2021 09:36:00 -0500 Received: from szxga06-in.huawei.com ([45.249.212.32]:12947 "EHLO szxga06-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231650AbhBWOfl (ORCPT ); Tue, 23 Feb 2021 09:35:41 -0500 Received: from DGGEMS405-HUB.china.huawei.com (unknown [172.30.72.58]) by szxga06-in.huawei.com (SkyGuard) with ESMTP id 4DlM3m0cfWzjPqq; Tue, 23 Feb 2021 22:33:24 +0800 (CST) Received: from code-website.localdomain (10.175.127.227) by DGGEMS405-HUB.china.huawei.com (10.3.19.205) with Microsoft SMTP Server id 14.3.498.0; Tue, 23 Feb 2021 22:34:33 +0800 From: Zheng Yejian To: , , , CC: , , , Subject: [PATCH 4.9.y 1/1] futex: Fix OWNER_DEAD fixup Date: Tue, 23 Feb 2021 22:41:51 +0800 Message-ID: <20210223144151.916675-2-zhengyejian1@huawei.com> X-Mailer: git-send-email 2.25.4 In-Reply-To: <20210223144151.916675-1-zhengyejian1@huawei.com> References: <20210223144151.916675-1-zhengyejian1@huawei.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Content-Type: text/plain; charset=US-ASCII X-Originating-IP: [10.175.127.227] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Peter Zijlstra commit a97cb0e7b3f4c6297fd857055ae8e895f402f501 upstream. Both Geert and DaveJ reported that the recent futex commit: c1e2f0eaf015 ("futex: Avoid violating the 10th rule of futex") introduced a problem with setting OWNER_DEAD. We set the bit on an uninitialized variable and then entirely optimize it away as a dead-store. Move the setting of the bit to where it is more useful. Reported-by: Geert Uytterhoeven Reported-by: Dave Jones Signed-off-by: Peter Zijlstra (Intel) Cc: Andrew Morton Cc: Linus Torvalds Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Thomas Gleixner Fixes: c1e2f0eaf015 ("futex: Avoid violating the 10th rule of futex") Link: http://lkml.kernel.org/r/20180122103947.GD2228@hirez.programming.kicks-ass.net Signed-off-by: Ingo Molnar Signed-off-by: Zheng Yejian --- kernel/futex.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/kernel/futex.c b/kernel/futex.c index b65dbb5d60bb..604d1cb9839d 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -2424,9 +2424,6 @@ static int __fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q, int err = 0; oldowner = pi_state->owner; - /* Owner died? */ - if (!pi_state->owner) - newtid |= FUTEX_OWNER_DIED; /* * We are here because either: @@ -2484,6 +2481,9 @@ static int __fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q, } newtid = task_pid_vnr(newowner) | FUTEX_WAITERS; + /* Owner died? */ + if (!pi_state->owner) + newtid |= FUTEX_OWNER_DIED; if (get_futex_value_locked(&uval, uaddr)) goto handle_fault; -- 2.25.4