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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,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 EBBB8C04EB8 for ; Tue, 4 Dec 2018 20:32:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 91DC42082B for ; Tue, 4 Dec 2018 20:32:02 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 91DC42082B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726240AbeLDUcB (ORCPT ); Tue, 4 Dec 2018 15:32:01 -0500 Received: from mx1.redhat.com ([209.132.183.28]:32896 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725919AbeLDUcA (ORCPT ); Tue, 4 Dec 2018 15:32:00 -0500 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 1A88130026BA; Tue, 4 Dec 2018 20:32:00 +0000 (UTC) Received: from llong.remote.csb (dhcp-17-55.bos.redhat.com [10.18.17.55]) by smtp.corp.redhat.com (Postfix) with ESMTP id 491D85DD8A; Tue, 4 Dec 2018 20:31:59 +0000 (UTC) Subject: Re: [PATCH v2 16/24] locking/lockdep: Retain the class key and name while freeing a lock class To: Bart Van Assche , mingo@redhat.com Cc: peterz@infradead.org, tj@kernel.org, johannes.berg@intel.com, linux-kernel@vger.kernel.org, Johannes Berg References: <20181204002833.55452-1-bvanassche@acm.org> <20181204002833.55452-17-bvanassche@acm.org> <4eb2d1ad-14ee-0080-7736-aefdf69b4f29@redhat.com> <1543950509.185366.197.camel@acm.org> From: Waiman Long Openpgp: preference=signencrypt Autocrypt: addr=longman@redhat.com; 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Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <1543950509.185366.197.camel@acm.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.47]); Tue, 04 Dec 2018 20:32:00 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/04/2018 02:08 PM, Bart Van Assche wrote: > On Tue, 2018-12-04 at 13:57 -0500, Waiman Long wrote: >> On 12/03/2018 07:28 PM, Bart Van Assche wrote: >>> The next patch in this series uses the class name in code that >>> detects lock class use-after-free. Hence retain the class name for >>> lock classes that are being freed. >>> >>> Cc: Peter Zijlstra >>> Cc: Waiman Long >>> Cc: Johannes Berg >>> Signed-off-by: Bart Van Assche >>> --- >>> kernel/locking/lockdep.c | 4 +--- >>> 1 file changed, 1 insertion(+), 3 deletions(-) >>> >>> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c >>> index ecd92969674c..92bdb187987f 100644 >>> --- a/kernel/locking/lockdep.c >>> +++ b/kernel/locking/lockdep.c >>> @@ -4147,10 +4147,8 @@ static void zap_class(struct lock_class *class) >>> * Unhash the class and remove it from the all_lock_classes list: >>> */ >>> hlist_del_rcu(&class->hash_entry); >>> + class->hash_entry.pprev = NULL; >>> list_del(&class->lock_entry); >>> -page >>> - RCU_INIT_POINTER(class->key, NULL); >>> - RCU_INIT_POINTER(class->name, NULL); >>> } >>> >>> static inline int within(const void *addr, void *start, unsigned long size) >> Using the name after module unload can be problematic if it points to >> memory space occupied by the unloaded kernel module. The memory page may >> be invalid with the potential of crashing the kernel. You may have to >> duplicate the name if it is really from the module address space. > The class name shouldn't be used by any of the code I introduced in the > lockdep infrastructure after unloading a kernel module finished unless if > some of the kernel module code is still running after unloading the kernel > module finished. I think if that happens that the kernel module author is > to blame and not lockdep :-) > > Bart. You do use the name once in a WARN_ON check in check_prev_add(). You commit log did say the class name will be used. -Longman