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=-12.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_PASS 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 8B53FC10F11 for ; Wed, 10 Apr 2019 12:13:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 600972083E for ; Wed, 10 Apr 2019 12:13:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731776AbfDJMNy (ORCPT ); Wed, 10 Apr 2019 08:13:54 -0400 Received: from terminus.zytor.com ([198.137.202.136]:52155 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727497AbfDJMNx (ORCPT ); Wed, 10 Apr 2019 08:13:53 -0400 Received: from terminus.zytor.com (localhost [127.0.0.1]) by terminus.zytor.com (8.15.2/8.15.2) with ESMTPS id x3ACDEVh764902 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Wed, 10 Apr 2019 05:13:14 -0700 Received: (from tipbot@localhost) by terminus.zytor.com (8.15.2/8.15.2/Submit) id x3ACDBFI764899; Wed, 10 Apr 2019 05:13:11 -0700 Date: Wed, 10 Apr 2019 05:13:11 -0700 X-Authentication-Warning: terminus.zytor.com: tipbot set sender to tipbot@zytor.com using -f From: tip-bot for Bart Van Assche Message-ID: Cc: shhuiw@foxmail.com, tglx@linutronix.de, longman@redhat.com, mingo@kernel.org, hpa@zytor.com, bvanassche@acm.org, peterz@infradead.org, will.deacon@arm.com, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org Reply-To: shhuiw@foxmail.com, longman@redhat.com, tglx@linutronix.de, mingo@kernel.org, hpa@zytor.com, bvanassche@acm.org, peterz@infradead.org, will.deacon@arm.com, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org In-Reply-To: <20190403233552.124673-1-bvanassche@acm.org> References: <20190403233552.124673-1-bvanassche@acm.org> To: linux-tip-commits@vger.kernel.org Subject: [tip:locking/urgent] locking/lockdep: Zap lock classes even with lock debugging disabled Git-Commit-ID: 90c1cba2b3b3851c151229f61801919b2904d437 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 90c1cba2b3b3851c151229f61801919b2904d437 Gitweb: https://git.kernel.org/tip/90c1cba2b3b3851c151229f61801919b2904d437 Author: Bart Van Assche AuthorDate: Wed, 3 Apr 2019 16:35:52 -0700 Committer: Ingo Molnar CommitDate: Wed, 10 Apr 2019 13:45:59 +0200 locking/lockdep: Zap lock classes even with lock debugging disabled The following commit: a0b0fd53e1e6 ("locking/lockdep: Free lock classes that are no longer in use") changed the behavior of lockdep_free_key_range() from unconditionally zapping lock classes into only zapping lock classes if debug_lock == true. Not zapping lock classes if debug_lock == false leaves dangling pointers in several lockdep datastructures, e.g. lock_class::name in the all_lock_classes list. The shell command "cat /proc/lockdep" causes the kernel to iterate the all_lock_classes list. Hence the "unable to handle kernel paging request" cash that Shenghui encountered by running cat /proc/lockdep. Since the new behavior can cause cat /proc/lockdep to crash, restore the pre-v5.1 behavior. This patch avoids that cat /proc/lockdep triggers the following crash with debug_lock == false: BUG: unable to handle kernel paging request at fffffbfff40ca448 RIP: 0010:__asan_load1+0x28/0x50 Call Trace: string+0xac/0x180 vsnprintf+0x23e/0x820 seq_vprintf+0x82/0xc0 seq_printf+0x92/0xb0 print_name+0x34/0xb0 l_show+0x184/0x200 seq_read+0x59e/0x6c0 proc_reg_read+0x11f/0x170 __vfs_read+0x4d/0x90 vfs_read+0xc5/0x1f0 ksys_read+0xab/0x130 __x64_sys_read+0x43/0x50 do_syscall_64+0x71/0x210 entry_SYSCALL_64_after_hwframe+0x49/0xbe Reported-by: shenghui Signed-off-by: Bart Van Assche Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Waiman Long Cc: Will Deacon Fixes: a0b0fd53e1e6 ("locking/lockdep: Free lock classes that are no longer in use") # v5.1-rc1. Link: https://lkml.kernel.org/r/20190403233552.124673-1-bvanassche@acm.org Signed-off-by: Ingo Molnar --- kernel/locking/lockdep.c | 29 ++++++++++++----------------- 1 file changed, 12 insertions(+), 17 deletions(-) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 34cdcbedda49..e16766ff184b 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -4689,8 +4689,8 @@ static void free_zapped_rcu(struct rcu_head *ch) return; raw_local_irq_save(flags); - if (!graph_lock()) - goto out_irq; + arch_spin_lock(&lockdep_lock); + current->lockdep_recursion = 1; /* closed head */ pf = delayed_free.pf + (delayed_free.index ^ 1); @@ -4702,8 +4702,8 @@ static void free_zapped_rcu(struct rcu_head *ch) */ call_rcu_zapped(delayed_free.pf + delayed_free.index); - graph_unlock(); -out_irq: + current->lockdep_recursion = 0; + arch_spin_unlock(&lockdep_lock); raw_local_irq_restore(flags); } @@ -4744,21 +4744,17 @@ static void lockdep_free_key_range_reg(void *start, unsigned long size) { struct pending_free *pf; unsigned long flags; - int locked; init_data_structures_once(); raw_local_irq_save(flags); - locked = graph_lock(); - if (!locked) - goto out_irq; - + arch_spin_lock(&lockdep_lock); + current->lockdep_recursion = 1; pf = get_pending_free(); __lockdep_free_key_range(pf, start, size); call_rcu_zapped(pf); - - graph_unlock(); -out_irq: + current->lockdep_recursion = 0; + arch_spin_unlock(&lockdep_lock); raw_local_irq_restore(flags); /* @@ -4911,9 +4907,8 @@ void lockdep_unregister_key(struct lock_class_key *key) return; raw_local_irq_save(flags); - if (!graph_lock()) - goto out_irq; - + arch_spin_lock(&lockdep_lock); + current->lockdep_recursion = 1; pf = get_pending_free(); hlist_for_each_entry_rcu(k, hash_head, hash_entry) { if (k == key) { @@ -4925,8 +4920,8 @@ void lockdep_unregister_key(struct lock_class_key *key) WARN_ON_ONCE(!found); __lockdep_free_key_range(pf, key, 1); call_rcu_zapped(pf); - graph_unlock(); -out_irq: + current->lockdep_recursion = 0; + arch_spin_unlock(&lockdep_lock); raw_local_irq_restore(flags); /* Wait until is_dynamic_key() has finished accessing k->hash_entry. */