Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751415AbdGQM5x (ORCPT ); Mon, 17 Jul 2017 08:57:53 -0400 Received: from mail-oi0-f67.google.com ([209.85.218.67]:33029 "EHLO mail-oi0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751344AbdGQM5v (ORCPT ); Mon, 17 Jul 2017 08:57:51 -0400 MIME-Version: 1.0 In-Reply-To: References: <20170714120720.906842-1-arnd@arndb.de> <20170714120720.906842-15-arnd@arndb.de> From: Arnd Bergmann Date: Mon, 17 Jul 2017 14:57:50 +0200 X-Google-Sender-Auth: ZGJDPxLu1jvvrWuaNxuucftHkHI Message-ID: Subject: Re: [PATCH 14/22] [media] usbvision-i2c: fix format overflow warning To: Hans Verkuil Cc: Linux Kernel Mailing List , Mauro Carvalho Chehab , Greg Kroah-Hartman , Linus Torvalds , Guenter Roeck , Andrew Morton , Networking , "David S . Miller" , "James E . J . Bottomley" , "Martin K . Petersen" , linux-scsi , "the arch/x86 maintainers" , Sakari Ailus , Linux Media Mailing List Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1336 Lines: 27 On Mon, Jul 17, 2017 at 2:53 PM, Hans Verkuil wrote: > On 14/07/17 14:07, Arnd Bergmann wrote: >> gcc-7 notices that we copy a fixed length string into another >> string of the same size, with additional characters: >> >> drivers/media/usb/usbvision/usbvision-i2c.c: In function 'usbvision_i2c_register': >> drivers/media/usb/usbvision/usbvision-i2c.c:190:36: error: '%d' directive writing between 1 and 11 bytes into a region of size between 0 and 47 [-Werror=format-overflow=] >> sprintf(usbvision->i2c_adap.name, "%s-%d-%s", i2c_adap_template.name, >> ^~~~~~~~~~ >> drivers/media/usb/usbvision/usbvision-i2c.c:190:2: note: 'sprintf' output between 4 and 76 bytes into a destination of size 48 >> >> We know this is fine as the template name is always "usbvision", so >> we can easily avoid the warning by using this as the format string >> directly. > > Hmm, how about replacing sprintf by snprintf? That feels a lot safer (this is very > old code, it's not surprising it is still using sprintf). With snprintf(), you will still get a -Wformat-truncation warning. One of my patches disables that warning by default, but Mauro likes build-testing with "make W=1", so it would still show up then. However, we can do both: replace the string and use snprintf(). Arnd