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,URIBL_BLOCKED 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 6011DC04EB8 for ; Tue, 4 Dec 2018 18:57:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2F1C520834 for ; Tue, 4 Dec 2018 18:57:53 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2F1C520834 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 S1726203AbeLDS5v (ORCPT ); Tue, 4 Dec 2018 13:57:51 -0500 Received: from mx1.redhat.com ([209.132.183.28]:38108 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725797AbeLDS5v (ORCPT ); Tue, 4 Dec 2018 13:57:51 -0500 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id A262E3082B23; Tue, 4 Dec 2018 18:57:50 +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 C773560BF1; Tue, 4 Dec 2018 18:57:49 +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> 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: <20181204002833.55452-17-bvanassche@acm.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.45]); Tue, 04 Dec 2018 18:57:50 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Cheers, Longman