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

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] [day] [month] [year] [list]

Message-ID: <20210105035404.c47atgdsiqoa2wuc@vireshk-i7>
Date:   Tue, 5 Jan 2021 09:24:04 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Colin King <colin.king@...onical.com>
Cc:     "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Stephen Warren <swarren@...dia.com>, linux-pm@...r.kernel.org,
        kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] cpufreq: powernow-k8: add null check to policy to
 avoid null pointer dereference

On 04-01-21, 13:02, Colin King wrote:
> From: Colin Ian King <colin.king@...onical.com>
> 
> 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@...onical.com>
> ---
>  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