Re: [PATCH][next] cpufreq: powernow-k8: add null check to policy to avoid null pointer dereference

[Viresh Kumar]

On 04-01-21, 13:02, Colin King wrote:
> From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> 
> Currently there is an unlikely case where cpufreq_cpu_get returns a
> null policy and this will cause a null pointer dereference later on.
> Fix this by adding a null check and adding an error return.
> 
> Addresses-Coverity: ("Dereference null return")
> Fixes: b43a7ffbf33b ("cpufreq: Notify all policy->cpus in cpufreq_notify_transition()")
> Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> ---
>  drivers/cpufreq/powernow-k8.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/cpufreq/powernow-k8.c b/drivers/cpufreq/powernow-k8.c
> index 0acc9e241cd7..c5368545ba1f 100644
> --- a/drivers/cpufreq/powernow-k8.c
> +++ b/drivers/cpufreq/powernow-k8.c
> @@ -913,6 +913,8 @@ static int transition_frequency_fidvid(struct powernow_k8_data *data,

The caller already has a pointer to the policy, you should rather pass
that here instead of doing cpufreq_cpu_get/put.

>  	freqs.new = find_khz_freq_from_fid(fid);
>  
>  	policy = cpufreq_cpu_get(smp_processor_id());
> +	if (!policy)
> +		return 1;
>  	cpufreq_cpu_put(policy);
>  
>  	cpufreq_freq_transition_begin(policy, &freqs);
> -- 
> 2.29.2

-- 
viresh