linux-kernel - [RFC PATCH 12/19] cpufreq: fix locking of policy->rwsem in cpufreq_init

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Message-Id: <1452533760-13787-13-git-send-email-juri.lelli@arm.com>
Date:	Mon, 11 Jan 2016 17:35:53 +0000
From:	Juri Lelli <juri.lelli@....com>
To:	linux-kernel@...r.kernel.org
Cc:	linux-pm@...r.kernel.org, peterz@...radead.org, rjw@...ysocki.net,
	viresh.kumar@...aro.org, mturquette@...libre.com,
	steve.muckle@...aro.org, vincent.guittot@...aro.org,
	morten.rasmussen@....com, dietmar.eggemann@....com,
	juri.lelli@....com
Subject: [RFC PATCH 12/19] cpufreq: fix locking of policy->rwsem in cpufreq_init_policy

There are paths in cpufreq_init_policy where policy is used, but its rwsem
is not held.

Fix it.

Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc: Viresh Kumar <viresh.kumar@...aro.org>
Signed-off-by: Juri Lelli <juri.lelli@....com>
---
 drivers/cpufreq/cpufreq.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index e7fc5c9..2c7cc6c73 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -998,21 +998,24 @@ static int cpufreq_add_policy_cpu(struct cpufreq_policy *policy, unsigned int cp
 {
 	int ret = 0;
 
+	down_write(&policy->rwsem);
+
 	/* Has this CPU been taken care of already? */
-	if (cpumask_test_cpu(cpu, policy->cpus))
+	if (cpumask_test_cpu(cpu, policy->cpus)) {
+		up_write(&policy->rwsem);
 		return 0;
+	}
 
 	if (has_target()) {
 		ret = __cpufreq_governor(policy, CPUFREQ_GOV_STOP);
 		if (ret) {
+			up_write(&policy->rwsem);
 			pr_err("%s: Failed to stop governor\n", __func__);
 			return ret;
 		}
 	}
 
-	down_write(&policy->rwsem);
 	cpumask_set_cpu(cpu, policy->cpus);
-	up_write(&policy->rwsem);
 
 	if (has_target()) {
 		ret = __cpufreq_governor(policy, CPUFREQ_GOV_START);
@@ -1020,10 +1023,12 @@ static int cpufreq_add_policy_cpu(struct cpufreq_policy *policy, unsigned int cp
 			ret = __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS);
 
 		if (ret) {
+			up_write(&policy->rwsem);
 			pr_err("%s: Failed to start governor\n", __func__);
 			return ret;
 		}
 	}
+	up_write(&policy->rwsem);
 
 	return 0;
 }
-- 
2.2.2