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([2402:f000:1:1501:200:5efe:6505:d305]) by smtp.gmail.com with ESMTPSA id l70-v6sm3275845pge.64.2018.07.26.18.49.45 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 26 Jul 2018 18:49:47 -0700 (PDT) Subject: Re: [BUG] video: fbdev: broadsheetfb: Possible null function pointers To: Bartlomiej Zolnierkiewicz Cc: dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <2568790.PcaMMF1rzM@amdc3058> From: Jia-Ju Bai Message-ID: Date: Fri, 27 Jul 2018 09:49:41 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: <2568790.PcaMMF1rzM@amdc3058> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018/7/26 22:34, Bartlomiej Zolnierkiewicz wrote: > On Thursday, July 26, 2018 10:17:44 PM bai wrote: >> In Linux-4.16, drivers/video/fbdev/broadsheetfb.c, >> >> 158. static void broadsheet_mmio_send_cmdargs(...) { >> ...... >> 163. par->board->mmio_write(...); >> ...... >> 166. par->board->mmio_write(...); >> 167. } >> >> For x86 kernel configuration, I find that there is no assignment of the >> function pointer ".mmio_write" in the kernel code. >> So calling the function pointer in lines 163 and 166 may cause a null >> pointer dereference. >> >> In this file, there are many calls to this function pointer... > This is a platform driver and it won't be used on x86 (actually it is > used only by single ARM PXA board). The dependency for FB_BROADSHEET > in Kconfig file could be improved to i.e. > > depends on FB && (ARCH_PXA || COMPILE_TEST) > > but there is no bug there. Thanks for the reply :) So I want to submit a patch of updating Kconfig in drivers/video/fbdev/Kconfig: config FB_BROADSHEET tristate "E-Ink Broadsheet/Epson S1D13521 controller support" - depends on FB + depends on FB && (ARCH_PXA || COMPILE_TEST) select FB_SYS_FILLRECT select FB_SYS_COPYAREA select FB_SYS_IMAGEBLIT select FB_SYS_FOPS select FB_DEFERRED_IO Do you think it is okay? Best wishes, Jia-Ju Bai