From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-lj1-f177.google.com (mail-lj1-f177.google.com [209.85.208.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F33193FC2 for ; Fri, 27 Aug 2021 07:17:01 +0000 (UTC) Received: by mail-lj1-f177.google.com with SMTP id q21so9770604ljj.6 for ; Fri, 27 Aug 2021 00:17:01 -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=Mll16f5ig54QTH1K375AxC++r155tFyVTQR0fs1QoYQtYI8KQkAsm5WG9tp2Etb3yH xGvgrPJZXrQLaJQRw6OEOUqD1X/fMHk3nBgGSEE0wY2uKoXkPyaeHkLrAZ/Ktep6IgO1 LzmB3DdqT0JXeEtROVrtOQoTjiepKx566beaF03gtzjShjEtfUe7qYEVXQyGJyGW294U NS3haCFt/FJzsG7cAzG2kgpIHB0g5E2YNzTZzUahJZzUJOpCn3v1QkgZWKGee/mIushv Ve/toeuB9SYWuRSnjCX6y1QyhDV5Y+xwQokwTDZH7IcNzNHiLG4GBtTaxpD1EzKo4l2z qVvg== X-Gm-Message-State: AOAM531QsEIi39NPDyBuzVZXRxqc+I8v7eVhFpeRBdWXnqj2tJXnphhy hjKJFqA/eQiS3n93TdDAGW0= 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 Precedence: bulk X-Mailing-List: linux-staging@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit 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