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

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Message-Id: <20210104130227.35354-1-colin.king@canonical.com>
Date:   Mon,  4 Jan 2021 13:02:27 +0000
From:   Colin King <colin.king@...onical.com>
To:     "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Stephen Warren <swarren@...dia.com>, linux-pm@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH][next] cpufreq: powernow-k8: add null check to policy to avoid null pointer dereference

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,
 	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