]> asedeno.scripts.mit.edu Git - linux.git/commitdiff
cpufreq: governor: Avoid accessing invalid governor_data
authorHenry Willard <henry.willard@oracle.com>
Wed, 15 Aug 2018 00:01:02 +0000 (17:01 -0700)
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>
Thu, 16 Aug 2018 21:03:29 +0000 (23:03 +0200)
If cppc_cpufreq.ko is deleted at the same time that tuned-adm is
changing profiles, there is a small chance that a race can occur
between cpufreq_dbs_governor_exit() and cpufreq_dbs_governor_limits()
resulting in a system failure when the latter tries to use
policy->governor_data that has been freed by the former.

This patch uses gov_dbs_data_mutex to synchronize access.

Fixes: e788892ba3cc (cpufreq: governor: Get rid of governor events)
Signed-off-by: Henry Willard <henry.willard@oracle.com>
[ rjw: Subject, minor white space adjustment ]
Cc: 4.8+ <stable@vger.kernel.org> # 4.8+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
drivers/cpufreq/cpufreq_governor.c

index 1d50e97d49f192cd8bf1c5eb0ce569e9641cf43e..6d53f7d9fc7a92d415b507f9b8facdb3f4143b17 100644 (file)
@@ -555,12 +555,20 @@ EXPORT_SYMBOL_GPL(cpufreq_dbs_governor_stop);
 
 void cpufreq_dbs_governor_limits(struct cpufreq_policy *policy)
 {
-       struct policy_dbs_info *policy_dbs = policy->governor_data;
+       struct policy_dbs_info *policy_dbs;
+
+       /* Protect gov->gdbs_data against cpufreq_dbs_governor_exit() */
+       mutex_lock(&gov_dbs_data_mutex);
+       policy_dbs = policy->governor_data;
+       if (!policy_dbs)
+               goto out;
 
        mutex_lock(&policy_dbs->update_mutex);
        cpufreq_policy_apply_limits(policy);
        gov_update_sample_delay(policy_dbs, 0);
-
        mutex_unlock(&policy_dbs->update_mutex);
+
+out:
+       mutex_unlock(&gov_dbs_data_mutex);
 }
 EXPORT_SYMBOL_GPL(cpufreq_dbs_governor_limits);