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=-4.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 76F5AC432BE for ; Fri, 27 Aug 2021 07:17:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5034560FC4 for ; Fri, 27 Aug 2021 07:17:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244318AbhH0HRx (ORCPT ); Fri, 27 Aug 2021 03:17:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34398 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235220AbhH0HRv (ORCPT ); Fri, 27 Aug 2021 03:17:51 -0400 Received: from mail-lj1-x22e.google.com (mail-lj1-x22e.google.com [IPv6:2a00:1450:4864:20::22e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AB39FC061757 for ; Fri, 27 Aug 2021 00:17:02 -0700 (PDT) Received: by mail-lj1-x22e.google.com with SMTP id s12so9889168ljg.0 for ; Fri, 27 Aug 2021 00:17:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=nsfTnZeRT042LbD6vZ5TbEoeI++bi2xeLyIL6BeGEEc=; b=lifqIgLXIGjaD6dYmYO1cCnauEyIsHrHmGgjhqbLV+2Njy5zjS8JMR62cY3rOwb7fH yyxPLNm13vHDr8TEDdLoSm4vSoV5H51MHu4PY4mDBPyfgk2K7Y15iz07fohlYq+FUSHv 6QISkkplfRCRpEYAJNFqLM5PHwyeRTRehC4eYEnp/UUjZUM10SuvfPhLCJDEBMvxfjvJ JlRdoBAhTKhfpdfHqxX/07n5agRzpz9UC/IP/GMZR6zPpvXjPE9qU1Kh1tubRc1K4ojX rI31fm5sQ2WMposUUxZTowIiJ6mpMgtJLi3uT0cAj4TDnj8Dq5zpnlslnFksjeJMzOKW SlKw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=nsfTnZeRT042LbD6vZ5TbEoeI++bi2xeLyIL6BeGEEc=; b=oQUxwRWFSA0oP5YKD/OfDTd5ckpFlJMwi0QJesIfUyyDbRy1Gew1fdb0ZWnyShO+Ip creDOHSjoNgrVf+8uQ2HHaA3lD3sCii4QfXDjibQK+kJYNhmdK+wEDK8+byVMunOFKAx QbCwEal2CLrWbn+XooUON4n+qllyhJt3LFBHXdKnbieqcOedwzKX/Ot/OuGTAa+ZjKFv ihZz7Y04je6qfNUpYwrsmes8xuqKC0vDpkH2jRqFoGtmiEzIV0de66o28i8K6PgiEMzw BiWdg7Ubffoy0+9xVf+zKIku0JEkuYdaHQun3DffnSQ9b6zpivaMqqu6olovM0iyiWoV btxw== X-Gm-Message-State: AOAM532pb8Oi4eoWJyu03PZflXxyAHHBDPKCSAIFaYpkIbOBoTnkrBOW Yz4awSw1XAawVIsDo9ZVl1T4jcjau4U= X-Google-Smtp-Source: ABdhPJzAnlhBDftiPfGxc8SVk+moS9LcKuO4pMQItSfs2ORHL0nrTBqEFtnN4CwizXPTLBLPxF1ccA== X-Received: by 2002:a05:651c:894:: with SMTP id d20mr6295547ljq.483.1630048619964; Fri, 27 Aug 2021 00:16:59 -0700 (PDT) Received: from [192.168.1.11] ([46.235.66.127]) by smtp.gmail.com with ESMTPSA id q9sm558596lfn.170.2021.08.27.00.16.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 27 Aug 2021 00:16:59 -0700 (PDT) Subject: Re: [PATCH v3 5/6] staging: r8188eu: add error handling of rtw_read32 To: "gregkh@linuxfoundation.org" Cc: David Laight , "Larry.Finger@lwfinger.net" , "phil@philpotter.co.uk" , "straube.linux@gmail.com" , "fmdefrancesco@gmail.com" , "linux-staging@lists.linux.dev" , "linux-kernel@vger.kernel.org" References: <93bf46ce2d0ce12e94672acf28b64dc341fde038.1629789580.git.paskripkin@gmail.com> <27f5e52d520b453cbcabb3d72f0f5d15@AcuMS.aculab.com> <20210826122221.5d2b0f37@gmail.com> <685618ac-8de1-4eb1-57dd-9d43b96e872e@gmail.com> <64112dfd8e8b472ab78ca8b4837dc9e9@AcuMS.aculab.com> <0eb2bbc6-9d35-9ff3-acde-fd89bbe0ca27@gmail.com> <6e864f9d133d4db3923190f5acacc32a@AcuMS.aculab.com> From: Pavel Skripkin Message-ID: <014d213d-b038-f40f-80b0-f1d5adbdf947@gmail.com> Date: Fri, 27 Aug 2021 10:16:57 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/27/21 10:12 AM, gregkh@linuxfoundation.org wrote: > On Thu, Aug 26, 2021 at 11:03:04PM +0300, Pavel Skripkin wrote: >> On 8/26/21 1:59 PM, David Laight wrote: >> > From: Pavel Skripkin >> > > Sent: 26 August 2021 11:55 >> > > >> > > On 8/26/21 1:22 PM, David Laight wrote: >> > > > From: Pavel Skripkin >> > > >> Sent: 26 August 2021 10:28 >> > > >> >> > > >> On 8/26/21 12:22 PM, Pavel Skripkin wrote: >> > > >> > On Thu, 26 Aug 2021 08:51:23 +0000 >> > > >> > David Laight wrote: >> > > > ... >> > > >> >> ... >> > > >> >> > -static u32 usb_read32(struct intf_hdl *pintfhdl, u32 addr) >> > > >> >> > +static int usb_read32(struct intf_hdl *pintfhdl, u32 addr, u32 >> > > >> >> > *data) { >> > > >> >> > u8 requesttype; >> > > >> >> > u16 wvalue; >> > > >> >> > u16 len; >> > > >> >> > - __le32 data; >> > > >> >> > + int res; >> > > >> >> > + __le32 tmp; >> > > >> >> > + >> > > >> >> > + if (WARN_ON(unlikely(!data))) >> > > >> >> > + return -EINVAL; >> > > >> >> > >> > > >> >> >> > > >> >> Kill the NULL check - it is a silly coding error. >> > > >> >> An OOPS is just as easy to debug. >> > > >> >> >> > > >> > >> > > >> > >> > > >> > I don't think that one single driver should kill the whole system. It's >> > > >> > 100% an error, but kernel can recover from it (for example disconnect >> > > >> > the driver, since it's broken). >> > > >> > >> > > >> > >> > > >> > AFIAK, Greg and Linus do not like BUG_ONs in recoverable state... >> > > >> > Correct me, if I am wrong >> > > >> > >> > > >> Oops, I thought about BUG_ON() instead of WARN_ON(), sorry for >> > > >> confusion. My point is "we should not let the box boom". >> > > > >> > > > >> > > > There is no point checking for NULL that just can't happen. >> > > > In this case all the callers will pass the address of a local. >> > > > There really is no point checking. >> > > > >> > > >> > > We not always read in local variable, there are few places, where we >> > > read into passed buffer. >> > >> > It is still a very local coding bug. >> > >> > David >> > >> >> Sure, but is defensive programming so bad? > > Yes it is, for when it is not needed. > >> Greg, what your opinion about this NULL check? > > Never check for things that you know are not going to happen. Otherwise > the kernel would just be full of pointless checks everywhere. > > And why are you waiting for me to tell you this? Why do you not believe > David? > Just wanted to hear more opinions on this check. I believe David, but opinions of other people are important too, IMO With regards, Pavel Skripkin