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=-3.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=no 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 14A8DC43331 for ; Tue, 24 Mar 2020 16:31:17 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 65B182076F for ; Tue, 24 Mar 2020 16:31:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="Ri1Mc8OS" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 65B182076F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-18184-kernel-hardening=archiver.kernel.org@lists.openwall.com Received: (qmail 15725 invoked by uid 550); 24 Mar 2020 16:31:10 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Received: (qmail 15685 invoked from network); 24 Mar 2020 16:31:09 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585067456; bh=zN8a8ff6F93rxfbnXtH/OcB/Pb+dW43Yhgo3Ww7vWQ4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Ri1Mc8OSEm6cogEpBO9hMkaeRhw+6K3o1kbrSlsDZvoC1oDtJ66RRAd2oZcCz9/+7 ncW1j/AHt+aiuYCn0axZhfZskTLlbffchzCWAGIi8cx/puBhsRiVmJXW7eF3+QT6uz 2TWkycg6hCS+tNpkoVgHuQyEGoThdUGY6yjTqB7o= Date: Tue, 24 Mar 2020 17:30:54 +0100 From: Greg KH To: Will Deacon Cc: linux-kernel@vger.kernel.org, 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: Re: [RFC PATCH 04/21] timers: Use hlist_unhashed() instead of open-coding in timer_pending() Message-ID: <20200324163054.GA2518746@kroah.com> References: <20200324153643.15527-1-will@kernel.org> <20200324153643.15527-5-will@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200324153643.15527-5-will@kernel.org> On Tue, Mar 24, 2020 at 03:36:26PM +0000, Will Deacon wrote: > 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 Reviewed-by: Greg Kroah-Hartman