The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From 2a3eb51e30b9ac66fe1b75877627a7e4aaeca24a Mon Sep 17 00:00:00 2001
From: Henry Willard <henry.willard@xxxxxxxxxx>
Date: Tue, 14 Aug 2018 17:01:02 -0700
Subject: [PATCH] cpufreq: governor: Avoid accessing invalid governor_data
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@xxxxxxxxxx>
[ rjw: Subject, minor white space adjustment ]
Cc: 4.8+ <stable@xxxxxxxxxxxxxxx> # 4.8+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c
index 1d50e97d49f1..6d53f7d9fc7a 100644
--- a/drivers/cpufreq/cpufreq_governor.c
+++ b/drivers/cpufreq/cpufreq_governor.c
@@ -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);
