Re: [PATCH] KVM: X86: Fix dereference null cpufreq policy

[Paolo Bonzini]

On 02/03/20 08:15, Wanpeng Li wrote:
> From: Wanpeng Li <wanpengli@xxxxxxxxxxx>
> 
> cpufreq policy which is get by cpufreq_cpu_get() can be NULL if it is failure,
> this patch takes care of it.
> 
> Fixes: aaec7c03de (KVM: x86: avoid useless copy of cpufreq policy)
> Reported-by: Naresh Kamboju <naresh.kamboju@xxxxxxxxxx>
> Cc: Naresh Kamboju <naresh.kamboju@xxxxxxxxxx>
> Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>

My bad, I checked kobject_put but didn't check that kobj is first in
struct cpufreq_policy.

I think we should do this in cpufreq_cpu_put or, even better, move the
kobject struct first in struct cpufreq_policy.  Rafael, Viresh, any
objection?

Paolo

>  		policy = cpufreq_cpu_get(cpu);
> -		if (policy && policy->cpuinfo.max_freq)
> -			max_tsc_khz = policy->cpuinfo.max_freq;
> +		if (policy) {
> +			if (policy->cpuinfo.max_freq)
> +				max_tsc_khz = policy->cpuinfo.max_freq;
> +			cpufreq_cpu_put(policy);
> +		}