Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH] KVM: X86: Fix dereference null cpufreq policy
To:     Wanpeng Li <kernellwp@gmail.com>, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org
Cc:     Sean Christopherson <sean.j.christopherson@intel.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>,
        Naresh Kamboju <naresh.kamboju@linaro.org>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Viresh Kumar <viresh.kumar@linaro.org>
References: <1583133336-7832-1-git-send-email-wanpengli@tencent.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <ab51f6c9-a67d-0107-772a-7fe57a2319cf@redhat.com>
Date:   Mon, 2 Mar 2020 08:55:12 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.4.1
MIME-Version: 1.0
In-Reply-To: <1583133336-7832-1-git-send-email-wanpengli@tencent.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 02/03/20 08:15, Wanpeng Li wrote:
> From: Wanpeng Li <wanpengli@tencent.com>
> 
> 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@linaro.org>
> Cc: Naresh Kamboju <naresh.kamboju@linaro.org>
> Signed-off-by: Wanpeng Li <wanpengli@tencent.com>

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);
> +		}