From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753469AbaHKVaL (ORCPT ); Mon, 11 Aug 2014 17:30:11 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:39016 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751134AbaHKVaK (ORCPT ); Mon, 11 Aug 2014 17:30:10 -0400 Message-ID: <53E935DE.6050201@infradead.org> Date: Mon, 11 Aug 2014 14:30:06 -0700 From: Randy Dunlap User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Rickard Strandqvist CC: Chris Metcalf , "David S. Miller" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v2] tile: avoid errors from truncating long strings in mpipe gxio References: <1406383386-1400-1-git-send-email-rickard_strandqvist@spectrumdigital.se> <53E13D78.6000903@tilera.com> <201408061838.s76Ic6lV014201@farm-0039.internal.tilera.com> <53E32022.2090006@infradead.org> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/11/14 13:43, Rickard Strandqvist wrote: > 2014-08-07 8:43 GMT+02:00 Randy Dunlap : >> On 08/06/14 11:16, Chris Metcalf wrote: >>> Using strncpy() will just silently truncate long strings; we should >>> instead return an appropriate error. Using strlcpy() would suffer from >>> the same problem. Instead, use strnlen()+memcpy(), and add an >>> error-checking step to make sure the lengths are reasonable. >>> >>> I called the convenience wrapper strscpy(), and a case could be made for >>> making it more generic (possibly with a better name), but that seems >>> outside the scope of this initial commit. >> >> Well, having looked at the function before I read this comment, my first >> thought was that it should be added to lib/string.c for general >> availability. >> >>> >>> Signed-off-by: Chris Metcalf >>> --- >>> v2: use strnlen instead of strlen >>> >>> arch/tile/gxio/mpipe.c | 30 +++++++++++++++++++++++++----- >>> 1 file changed, 25 insertions(+), 5 deletions(-) >>> >>> diff --git a/arch/tile/gxio/mpipe.c b/arch/tile/gxio/mpipe.c >>> index 5301a9ffbae1..27a56be8d583 100644 >>> --- a/arch/tile/gxio/mpipe.c >>> +++ b/arch/tile/gxio/mpipe.c >>> @@ -29,6 +29,25 @@ >>> /* HACK: Avoid pointless "shadow" warnings. */ >>> #define link link_shadow >>> >>> +/* >>> + * Use this routine to avoid copying too-long strings. Unlike strncpy >>> + * or strlcpy, we don't enable programmers who don't check return codes; >>> + * partially-copied strings can be problematic. The routine returns >>> + * the total number of bytes copied (including the trailing NUL) or >>> + * zero if the buffer wasn't big enough. >>> + */ >>> +static size_t strscpy(char *dest, const char *src, size_t size) >>> +{ >>> + size_t ret = strnlen(src, size) + 1; >>> + if (ret > size) { >>> + if (size) >>> + dest[0] = '\0'; >>> + return 0; >>> + } >>> + memcpy(dest, src, ret); >>> + return ret; >>> +} >> >> -- >> ~Randy > > > Hi > > Sounds like a great idea! > > Do it Chris! Randy? Yeah, I don't have a better name for it, but I do think that it's the right thing to do. Thanks, -- ~Randy