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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8564FC04A6A for ; Thu, 3 Aug 2023 03:08:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231721AbjHCDIu (ORCPT ); Wed, 2 Aug 2023 23:08:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43996 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231557AbjHCDIp (ORCPT ); Wed, 2 Aug 2023 23:08:45 -0400 Received: from mail.nfschina.com (unknown [42.101.60.195]) by lindbergh.monkeyblade.net (Postfix) with SMTP id 175951BD9; Wed, 2 Aug 2023 20:08:43 -0700 (PDT) Received: from [172.30.11.106] (unknown [180.167.10.98]) by mail.nfschina.com (Maildata Gateway V2.8.8) with ESMTPSA id 374596082CF9F; Thu, 3 Aug 2023 11:08:35 +0800 (CST) Message-ID: <414e987b-df9f-53c9-6455-4a2d10f7fcf5@nfschina.com> Date: Thu, 3 Aug 2023 11:08:34 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.8.0 Subject: Re: [PATCH] fs: lockd: avoid possible wrong NULL parameter Content-Language: en-US To: Dan Carpenter Cc: chuck.lever@oracle.com, jlayton@kernel.org, neilb@suse.de, kolga@netapp.com, Dai.Ngo@oracle.com, tom@talpey.com, trond.myklebust@hammerspace.com, anna@kernel.org, nathan@kernel.org, ndesaulniers@google.com, trix@redhat.com, bfields@fieldses.org, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, kernel-janitors@vger.kernel.org X-MD-Sfrom: suhui@nfschina.com X-MD-SrcIP: 180.167.10.98 From: Su Hui In-Reply-To: <0bd584fd-74ac-4b08-ae03-12e329ab186e@kadam.mountain> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/8/2 18:41, Dan Carpenter wrote: > There was a big fight about memcpy() in 2010. > > https://lwn.net/Articles/416821/ > > It's sort of related but also sort of different. My understanding is > that the glibc memcpy() says that memcpy() always does a dereference so > it can delete all the NULL checks which come after. The linux kernel > uses -fno-delete-null-pointer-checks to turn this behavior off. Really big fight! This article seems talk about  problem that using memcpy() to copy overlapping regions. I'm not sure glibc memcpy does the check about NULL， but glibc printf does this check. "And GNU libc checks strings passed to printf for a %s placeholder for NULL, when the C standard says this is not allowed."[1] [1] https://lwn.net/Articles/416821/ > > regards, > dan carpenter