linux-kernel - Re: cpufreq_stats NULL deref on second system suspend

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 11 Sep 2013 16:44:37 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	Viresh Kumar <viresh.kumar@...aro.org>
CC:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Stephen Warren <swarren@...dotorg.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	cpufreq <cpufreq@...r.kernel.org>
Subject: Re: cpufreq_stats NULL deref on second system suspend

On 09/11/2013 04:15 PM, Viresh Kumar wrote:
> On 11 September 2013 16:14, Viresh Kumar <viresh.kumar@...aro.org> wrote:
>> But I would have solved it differently :)
>>
>> We don't really need to call update_policy_cpu() again and again
>> as we don't really need to update policy->cpu...
>>
>> Rather it would be better to just move following inside
>> cpufreq_policy_alloc():
> 
> Half written mail sent :(
> 
> What about moving following to cpufreq_policy_alloc():
> 
> policy->cpu = cpu;
> 
> ??
> 

Hmm? The problem is not about merely updating the policy->cpu field; the
main issue is that the existing code was not letting the cpufreq-stats
code know that we updated the policy->cpu under the hood. It is important
for cpufreq-stats to know this because it maintains the reference to its
stats structure by associating it with the policy->cpu. So if policy->cpu
changes under the hood, it loses track of its reference. So we need to
keep that code informed about changes to policy->cpu. Thus, we need to call
update_policy_cpu() in the CPU online path (during resume). I don't see
how we can skip that.

Regards,
Srivatsa S. Bhat

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/