From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758300AbbJ3DeM (ORCPT ); Thu, 29 Oct 2015 23:34:12 -0400 Received: from mx2.parallels.com ([199.115.105.18]:36354 "EHLO mx2.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758135AbbJ3DeK (ORCPT ); Thu, 29 Oct 2015 23:34:10 -0400 From: James Bottomley To: "andy.shevchenko@gmail.com" CC: "ulf.hansson@linaro.org" , "linux@rasmusvillemoes.dk" , "andriy.shevchenko@linux.intel.com" , "vkuznets@redhat.com" , "linux-kernel@vger.kernel.org" , "akpm@linux-foundation.org" , "keescook@chromium.org" Subject: Re: [PATCH v3 2/4] lib/string_helpers.c: protect string_get_size() against blk_size=0 Thread-Topic: [PATCH v3 2/4] lib/string_helpers.c: protect string_get_size() against blk_size=0 Thread-Index: AQHREmcyuq98ZTg6HkG6bAUDyFTYep6Di8sAgAAI/ACAAENpAA== Date: Fri, 30 Oct 2015 03:34:04 +0000 Message-ID: <1446176044.25009.17.camel@Odin.com> References: <1446136250-11507-1-git-send-email-vkuznets@redhat.com> <1446136250-11507-3-git-send-email-vkuznets@redhat.com> <1446159638.25009.5.camel@Odin.com> In-Reply-To: Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-mailer: Evolution 3.12.11 x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.81.1.219] Content-Type: text/plain; charset="utf-8" Content-ID: <7E225C38DB7D9F43976B97AD4E00A9C4@sw.swsoft.com> MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by mail.home.local id t9U3YGLY017669 On Fri, 2015-10-30 at 01:32 +0200, Andy Shevchenko wrote: > On Fri, Oct 30, 2015 at 1:00 AM, James Bottomley wrote: > > On Thu, 2015-10-29 at 17:30 +0100, Vitaly Kuznetsov wrote: > >> Division by zero happens if blk_size=0 is supplied to string_get_size(). > >> Add WARN_ON() and set size to 0 to report '0 B'. > >> > >> Signed-off-by: Vitaly Kuznetsov > >> --- > >> lib/string_helpers.c | 5 +++++ > >> 1 file changed, 5 insertions(+) > >> > >> diff --git a/lib/string_helpers.c b/lib/string_helpers.c > >> index f6c27dc..ff3575b 100644 > >> --- a/lib/string_helpers.c > >> +++ b/lib/string_helpers.c > >> @@ -50,6 +50,11 @@ void string_get_size(u64 size, u32 blk_size, const enum string_size_units units, > >> > >> tmp[0] = '\0'; > >> i = 0; > >> + > >> + /* Calling string_get_size() with blk_size=0 is wrong! */ > >> + if (WARN_ON(!blk_size)) > > > > Get rid of the WARN_ON; it's the standard thing to do for a partially > > connected device. Seeing zero is standard in a whole variety of > > situations. SCSI shims the zero but most other drivers don't. > > For *block* size? It will crash the kernel. I've checked, it wasn't > changed from the beginning (b9f28d863594). The standard signal for a drive error in capacity is zero size and zero block size. We have to take that case as standard without emitting scary warnings. James {.n++%ݶw{.n+{G{ayʇڙ,jfhz_(階ݢj"mG?&~iOzv^m ?I