From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-bw0-f46.google.com ([209.85.214.46]:42949 "EHLO mail-bw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756335Ab1CBRgY (ORCPT ); Wed, 2 Mar 2011 12:36:24 -0500 Received: by bwz15 with SMTP id 15so373221bwz.19 for ; Wed, 02 Mar 2011 09:36:23 -0800 (PST) Message-ID: <4D6E7FBC.6040805@mvista.com> Date: Wed, 02 Mar 2011 20:34:52 +0300 From: Sergei Shtylyov MIME-Version: 1.0 To: Ralf Baechle CC: John Crispin , Ralph Hempel , Wim Van Sebroeck , linux-mips@linux-mips.org, linux-watchdog@vger.kernel.org Subject: Re: [PATCH V2 05/10] MIPS: lantiq: add watchdog support References: <1298996006-15960-1-git-send-email-blogic@openwrt.org> <1298996006-15960-6-git-send-email-blogic@openwrt.org> <4D6E286D.9050100@mvista.com> <20110302142933.GA18221@linux-mips.org> In-Reply-To: <20110302142933.GA18221@linux-mips.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-watchdog-owner@vger.kernel.org List-Id: linux-watchdog@vger.kernel.org Hello. Ralf Baechle wrote: >>> + switch (cmd) { >>> + case WDIOC_GETSUPPORT: >>> + ret = copy_to_user((struct watchdog_info __user *)arg, &ident, >>> + sizeof(ident)) ? -EFAULT : 0; >> Doesn't copy_to_user() return 0 or -EFAULT? > No and that's a common cause of bugs. copy_{from,to}_user returns the > number of characters that could be be copied so the conversion to an > error code is needed here. But then the code above would be wrong. Actually, it returns the number of bytes that could NOT be copied as I now see. > The function takes a void argument and there is no benefit from casting > to the full struct watchdog_info __user * pointer type other than maybe > clarity to the human reader. Indeed. > Ralf WBR, Sergei