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Thu, 26 Aug 2021 13:03:06 -0700 (PDT) Subject: Re: [PATCH v3 5/6] staging: r8188eu: add error handling of rtw_read32 To: David Laight Cc: "Larry.Finger@lwfinger.net" , "phil@philpotter.co.uk" , "gregkh@linuxfoundation.org" , "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: Date: Thu, 26 Aug 2021 23:03:04 +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: <6e864f9d133d4db3923190f5acacc32a@AcuMS.aculab.com> 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 8/26/21 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? Greg, what your opinion about this NULL check? With regards, Pavel Skripkin