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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,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 45EB7C43331 for ; Tue, 24 Mar 2020 15:37:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1B10920714 for ; Tue, 24 Mar 2020 15:37:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585064224; bh=88VE/OFCJ68wUOdcxhSay8r/8S/aaN+bgGPAlwd52xA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Mq1rzIv/8urGtZDdrcVvqVqPQkGIuOTJcBqQwOSWAuOy0T15R64O0gWunXlP6OKs6 Ar2Bi6h/UAMZIVMz7ON/NPppEJ2IN9JOsPGJx7hT8DhdqCcqhRYPzFFAv3jGmTBZVh unsawj+uurRMe7nDq86RBexL/GfSAPWV21wKHCE0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728365AbgCXPhD (ORCPT ); Tue, 24 Mar 2020 11:37:03 -0400 Received: from mail.kernel.org ([198.145.29.99]:59616 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727216AbgCXPhC (ORCPT ); Tue, 24 Mar 2020 11:37:02 -0400 Received: from localhost.localdomain (236.31.169.217.in-addr.arpa [217.169.31.236]) (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 07E5120789; Tue, 24 Mar 2020 15:36:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585064221; bh=88VE/OFCJ68wUOdcxhSay8r/8S/aaN+bgGPAlwd52xA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=UuO6IgZnkaarA94D7wpwykQ4xoQZNyPAp3GcmAWUlOD959KpOUcsbLUXezUDq1gQu 1XHhKPHtJGTanA/aVzrgdyzwqYNOKDYyG5cXOEGOM3ofhkp37APz6Jwu7Cn4IkyuMp oaxy+sYGeiaeecR0vMVrEJtsNaDEtOQKUt7snBJU= From: Will Deacon To: linux-kernel@vger.kernel.org Cc: Will Deacon , Eric Dumazet , Jann Horn , Kees Cook , Maddie Stone , Marco Elver , "Paul E . McKenney" , Peter Zijlstra , Thomas Gleixner , kernel-team@android.com, kernel-hardening@lists.openwall.com Subject: [RFC PATCH 04/21] timers: Use hlist_unhashed() instead of open-coding in timer_pending() Date: Tue, 24 Mar 2020 15:36:26 +0000 Message-Id: <20200324153643.15527-5-will@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200324153643.15527-1-will@kernel.org> References: <20200324153643.15527-1-will@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org timer_pending() open-codes a version of hlist_unhashed() to check whether or not the 'timer' parameter has been queued in the timer wheel. KCSAN detects this as a racy operation and explodes at us: | BUG: KCSAN: data-race in del_timer / detach_if_pending | | write to 0xffff88808697d870 of 8 bytes by task 10 on cpu 0: | __hlist_del include/linux/list.h:764 [inline] | detach_timer kernel/time/timer.c:815 [inline] | detach_if_pending+0xcd/0x2d0 kernel/time/timer.c:832 | try_to_del_timer_sync+0x60/0xb0 kernel/time/timer.c:1226 | del_timer_sync+0x6b/0xa0 kernel/time/timer.c:1365 | schedule_timeout+0x2d2/0x6e0 kernel/time/timer.c:1896 | rcu_gp_fqs_loop+0x37c/0x580 kernel/rcu/tree.c:1639 | rcu_gp_kthread+0x143/0x230 kernel/rcu/tree.c:1799 | kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253 | ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352 | | read to 0xffff88808697d870 of 8 bytes by task 12060 on cpu 1: | del_timer+0x3b/0xb0 kernel/time/timer.c:1198 | sk_stop_timer+0x25/0x60 net/core/sock.c:2845 | inet_csk_clear_xmit_timers+0x69/0xa0 net/ipv4/inet_connection_sock.c:523 | tcp_clear_xmit_timers include/net/tcp.h:606 [inline] | tcp_v4_destroy_sock+0xa3/0x3f0 net/ipv4/tcp_ipv4.c:2096 | inet_csk_destroy_sock+0xf4/0x250 net/ipv4/inet_connection_sock.c:836 | tcp_close+0x6f3/0x970 net/ipv4/tcp.c:2497 | inet_release+0x86/0x100 net/ipv4/af_inet.c:427 | __sock_release+0x85/0x160 net/socket.c:590 | sock_close+0x24/0x30 net/socket.c:1268 | __fput+0x1e1/0x520 fs/file_table.c:280 | ____fput+0x1f/0x30 fs/file_table.c:313 | task_work_run+0xf6/0x130 kernel/task_work.c:113 | tracehook_notify_resume include/linux/tracehook.h:188 [inline] | exit_to_usermode_loop+0x2b4/0x2c0 arch/x86/entry/common.c:163 Replace the explicit 'pprev' pointer comparison in timer_pending() with a call to hlist_unhashed() and initialise the 'expires' timer field explicitly in do_init_timer() so that the compiler doesn't emit bogus 'maybe used uninitialised' warnings now that it cannot reason statically about the result of timer_pending(). Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Eric Dumazet Signed-off-by: Will Deacon --- include/linux/timer.h | 5 +++-- kernel/time/timer.c | 1 + 2 files changed, 4 insertions(+), 2 deletions(-) diff --git a/include/linux/timer.h b/include/linux/timer.h index 1e6650ed066d..e9610d2988ba 100644 --- a/include/linux/timer.h +++ b/include/linux/timer.h @@ -158,13 +158,14 @@ static inline void destroy_timer_on_stack(struct timer_list *timer) { } * * timer_pending will tell whether a given timer is currently pending, * or not. Callers must ensure serialization wrt. other operations done - * to this timer, eg. interrupt contexts, or other CPUs on SMP. + * to this timer, eg. interrupt contexts, or other CPUs on SMP if they + * cannot tolerate spurious results. * * return value: 1 if the timer is pending, 0 if not. */ static inline int timer_pending(const struct timer_list * timer) { - return timer->entry.pprev != NULL; + return !hlist_unhashed(&timer->entry); } extern void add_timer_on(struct timer_list *timer, int cpu); diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 4820823515e9..9e1c6fc8433a 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -780,6 +780,7 @@ static void do_init_timer(struct timer_list *timer, const char *name, struct lock_class_key *key) { timer->entry.pprev = NULL; + timer->expires = 0; /* Avoid bogus 'maybe used uninitialized' warning */ timer->function = func; timer->flags = flags | raw_smp_processor_id(); lockdep_init_map(&timer->lockdep_map, name, key, 0); -- 2.20.1