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Thu, 20 May 2021 10:01:54 -0700 (PDT) Received: from localhost ([2600:1700:e321:62f0:329c:23ff:fee3:9d7c]) by smtp.gmail.com with ESMTPSA id y8sm2312647qtn.61.2021.05.20.10.01.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 20 May 2021 10:01:53 -0700 (PDT) From: Guenter Roeck To: Derek Kiernan Cc: Dragan Cvetic , Arnd Bergmann , Greg Kroah-Hartman , Michal Simek , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Guenter Roeck Subject: [RFC PATCH] misc: xilinx-sdfec: Check if file->private_data is NULL Date: Thu, 20 May 2021 10:01:50 -0700 Message-Id: <20210520170150.1615956-1-linux@roeck-us.net> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210520_100156_630383_E744B4C8 X-CRM114-Status: GOOD ( 15.61 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org container_of() only returns NULL if the passed pointer is NULL _and_ the embedded element is the first element of the structure. Even if that is the case, testing against it is misleading and possibly dangerous because the position of the embedded element may change. Explicitly check if the parameter is NULL and bail out if so instead of checking the result of container_of(). Signed-off-by: Guenter Roeck --- RFC: The NULL check in the poll function is likely unnecessary. Interestingly, there is no NULL check in the ioctl function, even though there is a similar container_of() in that function. However, I do not feel comfortable enough to change the functionality of this code and drop the check entirely. drivers/misc/xilinx_sdfec.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/misc/xilinx_sdfec.c b/drivers/misc/xilinx_sdfec.c index 23c8448a9c3b..0a3721d31dea 100644 --- a/drivers/misc/xilinx_sdfec.c +++ b/drivers/misc/xilinx_sdfec.c @@ -1011,11 +1011,11 @@ static __poll_t xsdfec_poll(struct file *file, poll_table *wait) __poll_t mask = 0; struct xsdfec_dev *xsdfec; - xsdfec = container_of(file->private_data, struct xsdfec_dev, miscdev); - - if (!xsdfec) + if (!file->private_data) return EPOLLNVAL | EPOLLHUP; + xsdfec = container_of(file->private_data, struct xsdfec_dev, miscdev); + poll_wait(file, &xsdfec->waitq, wait); /* XSDFEC ISR detected an error */ -- 2.25.1 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel