From patchwork Fri Nov 17 23:52:56 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yuxuan Luo X-Patchwork-Id: 1865317 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@legolas.ozlabs.org Authentication-Results: legolas.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=lists.ubuntu.com (client-ip=185.125.189.65; helo=lists.ubuntu.com; envelope-from=kernel-team-bounces@lists.ubuntu.com; receiver=patchwork.ozlabs.org) Received: from lists.ubuntu.com (lists.ubuntu.com [185.125.189.65]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by legolas.ozlabs.org (Postfix) with ESMTPS id 4SXDJk5nfhz1yRb for ; Sat, 18 Nov 2023 10:54:14 +1100 (AEDT) Received: from localhost ([127.0.0.1] helo=lists.ubuntu.com) by lists.ubuntu.com with esmtp (Exim 4.86_2) (envelope-from ) id 1r48ev-0002Ju-NF; Fri, 17 Nov 2023 23:54:03 +0000 Received: from smtp-relay-internal-0.internal ([10.131.114.225] helo=smtp-relay-internal-0.canonical.com) by lists.ubuntu.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1r48ep-0002Gz-2J for kernel-team@lists.ubuntu.com; Fri, 17 Nov 2023 23:53:55 +0000 Received: from mail-pl1-f200.google.com (mail-pl1-f200.google.com [209.85.214.200]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by smtp-relay-internal-0.canonical.com (Postfix) with ESMTPS id C60A23F11F for ; Fri, 17 Nov 2023 23:53:54 +0000 (UTC) Received: by mail-pl1-f200.google.com with SMTP id d9443c01a7336-1cc237c79f1so32151175ad.2 for ; Fri, 17 Nov 2023 15:53:54 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1700265233; x=1700870033; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=8vdgw8mDzbxi7bvfSviEySm6LeEi+BzSU1NKa3yU2pQ=; b=lDlIob7eDDrsqIW/DgMzQHWYDh+7yzuoRrIzQMlZCXYuKWpfeSnngadzFC5qdd1BDQ xTSEdJxyRpTBbmWHmtbCrhEioGTJHOHnT23Xzvk7Zyw0fZ5pmLZBdJfhEHqoueHLv+DD ZgwTAUAaOoZk1wCU//XCi6bFPCHiN4v6/5mSICtfEWsYzgVZx8fyNuUDY2cWrvvOab3N tKc9bqHgQH36X1Q8VbTFutJSaeestDm47Lxxf3Y9U/Dq/Fdv1nXcqTCmu1qovcQ0U9HS 47OV9uaGMftakW+Wgkk4qQKa1qZhTmx8OuO0e5qGY5vWHfgWVINjlTbbeqGJVrnKRR9e IGBQ== X-Gm-Message-State: AOJu0YxTz4no5N/gluw66HoAViaYdA9oqfRmYlmmbU2I8XxalDFHSpMJ IVQqfywlfVjQeYuNgTLjLbCT9fRmFLuMVL1mndWTxma3HP+TU0Nc+8NQFJ2haqL1IYgxxL0aFly w5rs5X78SRikn7MxxfCE2I01wbXy+NTjGcLYs+vJtODo7DspJ1w== X-Received: by 2002:a17:902:bd97:b0:1cc:5920:1d1c with SMTP id q23-20020a170902bd9700b001cc59201d1cmr1069257pls.48.1700265232853; Fri, 17 Nov 2023 15:53:52 -0800 (PST) X-Google-Smtp-Source: AGHT+IFqbZGV5dSragKP0B3ya32Nhkm5g4QbtiFB+SOGAL027SNFaoIwrli9z+k+g68HEqhpUHmWcw== X-Received: by 2002:a17:902:bd97:b0:1cc:5920:1d1c with SMTP id q23-20020a170902bd9700b001cc59201d1cmr1069247pls.48.1700265232338; Fri, 17 Nov 2023 15:53:52 -0800 (PST) Received: from localhost.localdomain ([2001:67c:1562:8007::aac:4795]) by smtp.gmail.com with ESMTPSA id y24-20020a170902b49800b001bb9d6b1baasm1884994plr.198.2023.11.17.15.53.50 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 17 Nov 2023 15:53:51 -0800 (PST) From: Yuxuan Luo To: kernel-team@lists.ubuntu.com Subject: [PATCH 05/11] timers: Split [try_to_]del_timer[_sync]() to prepare for shutdown mode Date: Fri, 17 Nov 2023 18:52:56 -0500 Message-Id: <20231117235302.79546-6-yuxuan.luo@canonical.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231117235302.79546-1-yuxuan.luo@canonical.com> References: <20231117235302.79546-1-yuxuan.luo@canonical.com> MIME-Version: 1.0 X-BeenThere: kernel-team@lists.ubuntu.com X-Mailman-Version: 2.1.20 Precedence: list List-Id: Kernel team discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kernel-team-bounces@lists.ubuntu.com Sender: "kernel-team" From: Thomas Gleixner Tearing down timers which have circular dependencies to other functionality, e.g. workqueues, where the timer can schedule work and work can arm timers, is not trivial. In those cases it is desired to shutdown the timer in a way which prevents rearming of the timer. The mechanism to do so is to set timer->function to NULL and use this as an indicator for the timer arming functions to ignore the (re)arm request. Split the inner workings of try_do_del_timer_sync(), del_timer_sync() and del_timer() into helper functions to prepare for implementing the shutdown functionality. No functional change. Co-developed-by: Steven Rostedt Signed-off-by: Steven Rostedt Signed-off-by: Thomas Gleixner Tested-by: Guenter Roeck Reviewed-by: Jacob Keller Reviewed-by: Anna-Maria Behnsen Link: https://lore.kernel.org/all/20220407161745.7d6754b3@gandalf.local.home Link: https://lore.kernel.org/all/20221110064101.429013735@goodmis.org Link: https://lore.kernel.org/r/20221123201625.195147423@linutronix.de (cherry picked from commit 8553b5f2774a66b1f293b7d783934210afb8f23c) CVE-2023-6039 Signed-off-by: Yuxuan Luo --- kernel/time/timer.c | 145 ++++++++++++++++++++++++++++---------------- 1 file changed, 93 insertions(+), 52 deletions(-) diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 9016721ff25e0..ef0aa26cc2c88 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -1202,20 +1202,14 @@ void add_timer_on(struct timer_list *timer, int cpu) EXPORT_SYMBOL_GPL(add_timer_on); /** - * timer_delete - Deactivate a timer + * __timer_delete - Internal function: Deactivate a timer * @timer: The timer to be deactivated * - * The function only deactivates a pending timer, but contrary to - * timer_delete_sync() it does not take into account whether the timer's - * callback function is concurrently executed on a different CPU or not. - * It neither prevents rearming of the timer. If @timer can be rearmed - * concurrently then the return value of this function is meaningless. - * * Return: * * %0 - The timer was not pending * * %1 - The timer was pending and deactivated */ -int timer_delete(struct timer_list *timer) +static int __timer_delete(struct timer_list *timer) { struct timer_base *base; unsigned long flags; @@ -1231,25 +1225,37 @@ int timer_delete(struct timer_list *timer) return ret; } -EXPORT_SYMBOL(timer_delete); /** - * try_to_del_timer_sync - Try to deactivate a timer - * @timer: Timer to deactivate + * timer_delete - Deactivate a timer + * @timer: The timer to be deactivated * - * This function tries to deactivate a timer. On success the timer is not - * queued and the timer callback function is not running on any CPU. + * The function only deactivates a pending timer, but contrary to + * timer_delete_sync() it does not take into account whether the timer's + * callback function is concurrently executed on a different CPU or not. + * It neither prevents rearming of the timer. If @timer can be rearmed + * concurrently then the return value of this function is meaningless. * - * This function does not guarantee that the timer cannot be rearmed right - * after dropping the base lock. That needs to be prevented by the calling - * code if necessary. + * Return: + * * %0 - The timer was not pending + * * %1 - The timer was pending and deactivated + */ +int timer_delete(struct timer_list *timer) +{ + return __timer_delete(timer); +} +EXPORT_SYMBOL(timer_delete); + +/** + * __try_to_del_timer_sync - Internal function: Try to deactivate a timer + * @timer: Timer to deactivate * * Return: * * %0 - The timer was not pending * * %1 - The timer was pending and deactivated * * %-1 - The timer callback function is running on a different CPU */ -int try_to_del_timer_sync(struct timer_list *timer) +static int __try_to_del_timer_sync(struct timer_list *timer) { struct timer_base *base; unsigned long flags; @@ -1266,6 +1272,27 @@ int try_to_del_timer_sync(struct timer_list *timer) return ret; } + +/** + * try_to_del_timer_sync - Try to deactivate a timer + * @timer: Timer to deactivate + * + * This function tries to deactivate a timer. On success the timer is not + * queued and the timer callback function is not running on any CPU. + * + * This function does not guarantee that the timer cannot be rearmed right + * after dropping the base lock. That needs to be prevented by the calling + * code if necessary. + * + * Return: + * * %0 - The timer was not pending + * * %1 - The timer was pending and deactivated + * * %-1 - The timer callback function is running on a different CPU + */ +int try_to_del_timer_sync(struct timer_list *timer) +{ + return __try_to_del_timer_sync(timer); +} EXPORT_SYMBOL(try_to_del_timer_sync); #ifdef CONFIG_PREEMPT_RT @@ -1342,45 +1369,15 @@ static inline void del_timer_wait_running(struct timer_list *timer) { } #endif /** - * timer_delete_sync - Deactivate a timer and wait for the handler to finish. + * __timer_delete_sync - Internal function: Deactivate a timer and wait + * for the handler to finish. * @timer: The timer to be deactivated * - * Synchronization rules: Callers must prevent restarting of the timer, - * otherwise this function is meaningless. It must not be called from - * interrupt contexts unless the timer is an irqsafe one. The caller must - * not hold locks which would prevent completion of the timer's callback - * function. The timer's handler must not call add_timer_on(). Upon exit - * the timer is not queued and the handler is not running on any CPU. - * - * For !irqsafe timers, the caller must not hold locks that are held in - * interrupt context. Even if the lock has nothing to do with the timer in - * question. Here's why:: - * - * CPU0 CPU1 - * ---- ---- - * - * call_timer_fn(); - * base->running_timer = mytimer; - * spin_lock_irq(somelock); - * - * spin_lock(somelock); - * timer_delete_sync(mytimer); - * while (base->running_timer == mytimer); - * - * Now timer_delete_sync() will never return and never release somelock. - * The interrupt on the other CPU is waiting to grab somelock but it has - * interrupted the softirq that CPU0 is waiting to finish. - * - * This function cannot guarantee that the timer is not rearmed again by - * some concurrent or preempting code, right after it dropped the base - * lock. If there is the possibility of a concurrent rearm then the return - * value of the function is meaningless. - * * Return: * * %0 - The timer was not pending * * %1 - The timer was pending and deactivated */ -int timer_delete_sync(struct timer_list *timer) +static int __timer_delete_sync(struct timer_list *timer) { int ret; @@ -1400,7 +1397,7 @@ int timer_delete_sync(struct timer_list *timer) * don't use it in hardirq context, because it * could lead to deadlock. */ - WARN_ON(in_irq() && !(timer->flags & TIMER_IRQSAFE)); + WARN_ON(in_hardirq() && !(timer->flags & TIMER_IRQSAFE)); /* * Must be able to sleep on PREEMPT_RT because of the slowpath in @@ -1410,7 +1407,7 @@ int timer_delete_sync(struct timer_list *timer) lockdep_assert_preemption_enabled(); do { - ret = try_to_del_timer_sync(timer); + ret = __try_to_del_timer_sync(timer); if (unlikely(ret < 0)) { del_timer_wait_running(timer); @@ -1420,6 +1417,50 @@ int timer_delete_sync(struct timer_list *timer) return ret; } + +/** + * timer_delete_sync - Deactivate a timer and wait for the handler to finish. + * @timer: The timer to be deactivated + * + * Synchronization rules: Callers must prevent restarting of the timer, + * otherwise this function is meaningless. It must not be called from + * interrupt contexts unless the timer is an irqsafe one. The caller must + * not hold locks which would prevent completion of the timer's callback + * function. The timer's handler must not call add_timer_on(). Upon exit + * the timer is not queued and the handler is not running on any CPU. + * + * For !irqsafe timers, the caller must not hold locks that are held in + * interrupt context. Even if the lock has nothing to do with the timer in + * question. Here's why:: + * + * CPU0 CPU1 + * ---- ---- + * + * call_timer_fn(); + * base->running_timer = mytimer; + * spin_lock_irq(somelock); + * + * spin_lock(somelock); + * timer_delete_sync(mytimer); + * while (base->running_timer == mytimer); + * + * Now timer_delete_sync() will never return and never release somelock. + * The interrupt on the other CPU is waiting to grab somelock but it has + * interrupted the softirq that CPU0 is waiting to finish. + * + * This function cannot guarantee that the timer is not rearmed again by + * some concurrent or preempting code, right after it dropped the base + * lock. If there is the possibility of a concurrent rearm then the return + * value of the function is meaningless. + * + * Return: + * * %0 - The timer was not pending + * * %1 - The timer was pending and deactivated + */ +int timer_delete_sync(struct timer_list *timer) +{ + return __timer_delete_sync(timer); +} EXPORT_SYMBOL(timer_delete_sync); static void call_timer_fn(struct timer_list *timer,