From mboxrd@z Thu Jan 1 00:00:00 1970 From: sudeep.holla@arm.com (Sudeep Holla) Date: Thu, 6 Sep 2018 18:11:56 +0100 Subject: [PATCH v2] firmware: arm_scmi: fix divide by zero when sustained_perf_level is zero In-Reply-To: <20180906165932.csa5b4vlmaekv5y2@localhost> References: <1536165491-27813-1-git-send-email-sudeep.holla@arm.com> <1536246639-7420-1-git-send-email-sudeep.holla@arm.com> <20180906165932.csa5b4vlmaekv5y2@localhost> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.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