From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B6256C10F25 for ; Wed, 11 Mar 2020 07:24:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 97B9B208C3 for ; Wed, 11 Mar 2020 07:24:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728416AbgCKHYx (ORCPT ); Wed, 11 Mar 2020 03:24:53 -0400 Received: from mx2.suse.de ([195.135.220.15]:41650 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726672AbgCKHYx (ORCPT ); Wed, 11 Mar 2020 03:24:53 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 89652AC69; Wed, 11 Mar 2020 07:24:51 +0000 (UTC) Date: Wed, 11 Mar 2020 08:24:51 +0100 Message-ID: From: Takashi Iwai To: Greg Kroah-Hartman Cc: "Rafael J . Wysocki" , linux-kernel@vger.kernel.org Subject: Re: [PATCH] drivers/base/cpu: Use scnprintf() for avoiding potential buffer overflow In-Reply-To: <20200311071935.GA3656396@kroah.com> References: <20200311071200.4024-1-tiwai@suse.de> <20200311071935.GA3656396@kroah.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 Emacs/25.3 (x86_64-suse-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 11 Mar 2020 08:19:35 +0100, Greg Kroah-Hartman wrote: > > On Wed, Mar 11, 2020 at 08:12:00AM +0100, Takashi Iwai wrote: > > Since snprintf() returns the would-be-output size instead of the > > actual output size, the succeeding calls may go beyond the given > > buffer limit. Fix it by replacing with scnprintf(). > > > > Signed-off-by: Takashi Iwai > > --- > > drivers/base/cpu.c | 8 ++++---- > > 1 file changed, 4 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c > > index 6265871a4af2..0abcd9d68714 100644 > > --- a/drivers/base/cpu.c > > +++ b/drivers/base/cpu.c > > @@ -231,7 +231,7 @@ static struct cpu_attr cpu_attrs[] = { > > static ssize_t print_cpus_kernel_max(struct device *dev, > > struct device_attribute *attr, char *buf) > > { > > - int n = snprintf(buf, PAGE_SIZE-2, "%d\n", NR_CPUS - 1); > > + int n = scnprintf(buf, PAGE_SIZE-2, "%d\n", NR_CPUS - 1); > > This should just be "sprintf()" as we "know" that fitting a single > number will work. > > > return n; > > } > > static DEVICE_ATTR(kernel_max, 0444, print_cpus_kernel_max, NULL); > > @@ -258,13 +258,13 @@ static ssize_t print_cpus_offline(struct device *dev, > > buf[n++] = ','; > > > > if (nr_cpu_ids == total_cpus-1) > > - n += snprintf(&buf[n], len - n, "%u", nr_cpu_ids); > > + n += scnprintf(&buf[n], len - n, "%u", nr_cpu_ids); > > else > > - n += snprintf(&buf[n], len - n, "%u-%d", > > + n += scnprintf(&buf[n], len - n, "%u-%d", > > nr_cpu_ids, total_cpus-1); > > } > > > > - n += snprintf(&buf[n], len - n, "\n"); > > + n += scnprintf(&buf[n], len - n, "\n"); > > this part looks sane, can you respin this? OK, will do it. Thanks for a quick review! Takashi