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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0B205C433EF for ; Wed, 19 Jan 2022 14:44:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1355226AbiASOoH (ORCPT ); Wed, 19 Jan 2022 09:44:07 -0500 Received: from foss.arm.com ([217.140.110.172]:58214 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1355133AbiASOoG (ORCPT ); Wed, 19 Jan 2022 09:44:06 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 42849ED1; Wed, 19 Jan 2022 06:44:04 -0800 (PST) Received: from bogus (unknown [10.57.34.234]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id DEC5B3F774; Wed, 19 Jan 2022 06:44:01 -0800 (PST) Date: Wed, 19 Jan 2022 14:43:28 +0000 From: Sudeep Holla To: Bjorn Andersson Cc: Greg Kroah-Hartman , "Rafael J. Wysocki" , Viresh Kumar , Sudeep Holla , Lukasz Luba , Vladimir Zapolskiy , Thara Gopinath , linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-pm@vger.kernel.org Subject: Re: [PATCH 2/2] arch_topology: Sanity check cpumask in thermal pressure update Message-ID: <20220119144328.cvt76mhsufxg7qbr@bogus> References: <20220118185612.2067031-1-bjorn.andersson@linaro.org> <20220118185612.2067031-2-bjorn.andersson@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220118185612.2067031-2-bjorn.andersson@linaro.org> Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On Tue, Jan 18, 2022 at 10:56:12AM -0800, Bjorn Andersson wrote: > Occasionally during boot the Qualcomm cpufreq driver was able to cause > an invalid memory access in topology_update_thermal_pressure() on the > line: > > if (max_freq <= capped_freq) > > It turns out that this was caused by a race, which resulted in the > cpumask passed to the function being empty, in which case > cpumask_first() will return a cpu beyond the number of valid cpus, which > when used to access the per_cpu max_freq would return invalid pointer. > > The bug in the Qualcomm cpufreq driver is being fixed, but having a > sanity check of the arguments would have saved quite a bit of time and > it's not unlikely that others will run into the same issue. > > Signed-off-by: Bjorn Andersson > --- > drivers/base/arch_topology.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c > index 976154140f0b..6560a0c3b969 100644 > --- a/drivers/base/arch_topology.c > +++ b/drivers/base/arch_topology.c > @@ -177,6 +177,9 @@ void topology_update_thermal_pressure(const struct cpumask *cpus, > u32 max_freq; > int cpu; > > + if (WARN_ON(cpumask_empty(cpus))) > + return; > + Why can't the caller check and call this only when cpus is not empty ? IIUC there are many such APIs that use cpumask and could result in similar issues if called with empty cpus. Probably we could add a note that cpus must not be empty if that helps the callers ? -- Regards, Sudeep