[PATCH] cpufreq: powernow-k8: avoid use after free issue in cpufreq_notify_transition()

[qiwuchen55]

From: chenqiwu <chenqiwu@xxxxxxxxxx>

There is a potential UAF issue in cpufreq_notify_transition() that the
cpufreq of current cpu has been released before using it. So we should
make a judgement and avoid it.

Signed-off-by: chenqiwu <chenqiwu@xxxxxxxxxx>
---
 drivers/cpufreq/powernow-k8.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/cpufreq/powernow-k8.c b/drivers/cpufreq/powernow-k8.c
index 2db2f17..7391eb0 100644
--- a/drivers/cpufreq/powernow-k8.c
+++ b/drivers/cpufreq/powernow-k8.c
@@ -913,6 +913,11 @@ 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) {
+		pr_debug("cpu %d: CPUFreq policy not found\n",
+			 smp_processor_id());
+		return 1;
+	}
 	cpufreq_cpu_put(policy);
 
 	cpufreq_freq_transition_begin(policy, &freqs);
-- 
1.9.1