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cpufreq: governor: Avoid accessing invalid governor_data

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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: e788892ba3 (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>
This commit is contained in:
Henry Willard 2018-08-14 17:01:02 -07:00 committed by Rafael J. Wysocki
parent b018fc9800
commit 2a3eb51e30
1 changed files with 10 additions and 2 deletions
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12
drivers/cpufreq/cpufreq_governor.c
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@ -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);