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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,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 14BCEC33C9B for ; Tue, 7 Jan 2020 21:14:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DA47620678 for ; Tue, 7 Jan 2020 21:14:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578431677; bh=VUtMeQKWQSIxCGS9aZYwceQXOd91vXhSxdYmNnp6R9Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=fQioH/YeO+V/wISlxiY5ssfvyJHCpMVDswaaC0dqEmirMbo8hInFxkwxGkhP3cDF2 GpONel1rETIivHPXmZ4kBKnukw8QoQ470Ufhw7+VjFfD/ssiXZ4eBm1KEPeMuPwEM2 uY1IFqAZohSomTB1EP2UHsgStkSgX8GaSoAP4j94= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727362AbgAGVJP (ORCPT ); Tue, 7 Jan 2020 16:09:15 -0500 Received: from mail.kernel.org ([198.145.29.99]:34366 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729336AbgAGVJN (ORCPT ); Tue, 7 Jan 2020 16:09:13 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 EAD9D2072A; Tue, 7 Jan 2020 21:09:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578431352; bh=VUtMeQKWQSIxCGS9aZYwceQXOd91vXhSxdYmNnp6R9Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=kSEfMWt5eFjbmM02IEvDXLebzWxjEg+En+YjlnSqr6ybd8otf8Kx82fgvo87urXJQ kju9zhkoi6pFHL2T3IH6Zk7H4WwFQKghPwYtArk11mWbm7DgpWd3Asyog0slbwrz9v szGjoERGUhr61NlsvByA84WjhCXZIVtzum0fd1YE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot+c5d03165a1bd1dead0c1@syzkaller.appspotmail.com, Christian Brauner , Marco Elver , Will Deacon , Andrea Parri , Dmitry Vyukov , Sasha Levin Subject: [PATCH 4.14 21/74] taskstats: fix data-race Date: Tue, 7 Jan 2020 21:54:46 +0100 Message-Id: <20200107205150.297768462@linuxfoundation.org> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200107205135.369001641@linuxfoundation.org> References: <20200107205135.369001641@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Christian Brauner [ Upstream commit 0b8d616fb5a8ffa307b1d3af37f55c15dae14f28 ] When assiging and testing taskstats in taskstats_exit() there's a race when setting up and reading sig->stats when a thread-group with more than one thread exits: write to 0xffff8881157bbe10 of 8 bytes by task 7951 on cpu 0: taskstats_tgid_alloc kernel/taskstats.c:567 [inline] taskstats_exit+0x6b7/0x717 kernel/taskstats.c:596 do_exit+0x2c2/0x18e0 kernel/exit.c:864 do_group_exit+0xb4/0x1c0 kernel/exit.c:983 get_signal+0x2a2/0x1320 kernel/signal.c:2734 do_signal+0x3b/0xc00 arch/x86/kernel/signal.c:815 exit_to_usermode_loop+0x250/0x2c0 arch/x86/entry/common.c:159 prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline] syscall_return_slowpath arch/x86/entry/common.c:274 [inline] do_syscall_64+0x2d7/0x2f0 arch/x86/entry/common.c:299 entry_SYSCALL_64_after_hwframe+0x44/0xa9 read to 0xffff8881157bbe10 of 8 bytes by task 7949 on cpu 1: taskstats_tgid_alloc kernel/taskstats.c:559 [inline] taskstats_exit+0xb2/0x717 kernel/taskstats.c:596 do_exit+0x2c2/0x18e0 kernel/exit.c:864 do_group_exit+0xb4/0x1c0 kernel/exit.c:983 __do_sys_exit_group kernel/exit.c:994 [inline] __se_sys_exit_group kernel/exit.c:992 [inline] __x64_sys_exit_group+0x2e/0x30 kernel/exit.c:992 do_syscall_64+0xcf/0x2f0 arch/x86/entry/common.c:296 entry_SYSCALL_64_after_hwframe+0x44/0xa9 Fix this by using smp_load_acquire() and smp_store_release(). Reported-by: syzbot+c5d03165a1bd1dead0c1@syzkaller.appspotmail.com Fixes: 34ec12349c8a ("taskstats: cleanup ->signal->stats allocation") Cc: stable@vger.kernel.org Signed-off-by: Christian Brauner Acked-by: Marco Elver Reviewed-by: Will Deacon Reviewed-by: Andrea Parri Reviewed-by: Dmitry Vyukov Link: https://lore.kernel.org/r/20191009114809.8643-1-christian.brauner@ubuntu.com Signed-off-by: Sasha Levin --- kernel/taskstats.c | 30 +++++++++++++++++++----------- 1 file changed, 19 insertions(+), 11 deletions(-) diff --git a/kernel/taskstats.c b/kernel/taskstats.c index 4559e914452b..390c76d4503c 100644 --- a/kernel/taskstats.c +++ b/kernel/taskstats.c @@ -568,25 +568,33 @@ static int taskstats_user_cmd(struct sk_buff *skb, struct genl_info *info) static struct taskstats *taskstats_tgid_alloc(struct task_struct *tsk) { struct signal_struct *sig = tsk->signal; - struct taskstats *stats; + struct taskstats *stats_new, *stats; - if (sig->stats || thread_group_empty(tsk)) - goto ret; + /* Pairs with smp_store_release() below. */ + stats = smp_load_acquire(&sig->stats); + if (stats || thread_group_empty(tsk)) + return stats; /* No problem if kmem_cache_zalloc() fails */ - stats = kmem_cache_zalloc(taskstats_cache, GFP_KERNEL); + stats_new = kmem_cache_zalloc(taskstats_cache, GFP_KERNEL); spin_lock_irq(&tsk->sighand->siglock); - if (!sig->stats) { - sig->stats = stats; - stats = NULL; + stats = sig->stats; + if (!stats) { + /* + * Pairs with smp_store_release() above and order the + * kmem_cache_zalloc(). + */ + smp_store_release(&sig->stats, stats_new); + stats = stats_new; + stats_new = NULL; } spin_unlock_irq(&tsk->sighand->siglock); - if (stats) - kmem_cache_free(taskstats_cache, stats); -ret: - return sig->stats; + if (stats_new) + kmem_cache_free(taskstats_cache, stats_new); + + return stats; } /* Send pid data out on exit */ -- 2.20.1