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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 250B1C433F5 for ; Thu, 6 Sep 2018 17:12:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DE63620844 for ; Thu, 6 Sep 2018 17:12:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DE63620844 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728661AbeIFVsZ (ORCPT ); Thu, 6 Sep 2018 17:48:25 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:48826 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726541AbeIFVsZ (ORCPT ); Thu, 6 Sep 2018 17:48:25 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 351427A9; Thu, 6 Sep 2018 10:11:59 -0700 (PDT) Received: from [10.4.12.116] (e107155-lin.Emea.Arm.com [10.4.12.116]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9EFBE3F557; Thu, 6 Sep 2018 10:11:57 -0700 (PDT) Cc: Sudeep Holla , arm@kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Ionela Voinescu , Quentin Perret , Kevin Hilman , Arnd Bergmann Subject: Re: [PATCH v2] firmware: arm_scmi: fix divide by zero when sustained_perf_level is zero To: Olof Johansson References: <1536165491-27813-1-git-send-email-sudeep.holla@arm.com> <1536246639-7420-1-git-send-email-sudeep.holla@arm.com> <20180906165932.csa5b4vlmaekv5y2@localhost> From: Sudeep Holla Organization: ARM Message-ID: Date: Thu, 6 Sep 2018 18:11:56 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180906165932.csa5b4vlmaekv5y2@localhost> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/09/18 17:59, Olof Johansson wrote: > Hi, > > On Thu, Sep 06, 2018 at 04:10:39PM +0100, Sudeep Holla wrote: >> Firmware can provide zero as values for sustained performance level and >> corresponding sustained frequency in kHz in order to hide the actual >> frequencies and provide only abstract values. It may endup with divide >> by zero scenario resulting in kernel panic. >> >> Let's set the multiplication factor to one if either one or both of them >> (sustained_perf_level and sustained_freq) are set to zero. >> >> Fixes: a9e3fbfaa0ff ("firmware: arm_scmi: add initial support for performance protocol") >> Reported-by: Ionela Voinescu >> Signed-off-by: Sudeep Holla >> --- >> drivers/firmware/arm_scmi/perf.c | 8 +++++++- >> 1 file changed, 7 insertions(+), 1 deletion(-) >> >> Hi ARM SoC team, >> >> Can you pick this patch directly ? > > Applied, however: > Thanks. >> diff --git a/drivers/firmware/arm_scmi/perf.c b/drivers/firmware/arm_scmi/perf.c >> index 721e6c57beae..64342944d917 100644 >> --- a/drivers/firmware/arm_scmi/perf.c >> +++ b/drivers/firmware/arm_scmi/perf.c >> @@ -166,7 +166,13 @@ scmi_perf_domain_attributes_get(const struct scmi_handle *handle, u32 domain, >> le32_to_cpu(attr->sustained_freq_khz); >> dom_info->sustained_perf_level = >> le32_to_cpu(attr->sustained_perf_level); >> - dom_info->mult_factor = (dom_info->sustained_freq_khz * 1000) / >> + if (!dom_info->sustained_freq_khz || >> + !dom_info->sustained_perf_level) >> + /* CPUFreq converts to kHz, hence default 1000 */ >> + dom_info->mult_factor = 1000; >> + else >> + dom_info->mult_factor = >> + (dom_info->sustained_freq_khz * 1000) / >> dom_info->sustained_perf_level; >> memcpy(dom_info->name, attr->name, SCMI_MAX_STR_SIZE); > > I noticed you do memcpy of these name strings in a few places, and use > it as a string. Any firmware that would return a non-terminated string > would cause problems later on. strlcpy() might be a better approach. > I seem to have assumed firmware always conforms to the definition: "Null terminated ASCII string of up to 16 bytes in length" when I initially wrote this. Thanks for the finding this and the suggestion, it's always safer to protect against firmware bugs. I will find all the occurrences and fix them. -- Regards, Sudeep