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author | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2016-02-18 01:19:00 (GMT) |
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committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2016-03-09 13:41:06 (GMT) |
commit | 574ef14d5dbcd2743326cc1b28e61a1e7733162a (patch) | |
tree | 7dbfd41fbfe7d59f2359d066fc823c119efaab59 | |
parent | 8eb055d3f53e52805907ea54e2eec0885be91a50 (diff) | |
download | linux-574ef14d5dbcd2743326cc1b28e61a1e7733162a.tar.xz |
cpufreq: governor: Close dbs_data update race condition
It is possible for a dbs_data object to be updated after its
usage counter has become 0. That may happen if governor_store()
runs (via a govenor tunable sysfs attribute write) in parallel
with cpufreq_governor_exit() called for the last cpufreq policy
associated with the dbs_data in question. In that case, if
governor_store() acquires dbs_data->mutex right after
cpufreq_governor_exit() has released it, the ->store() callback
invoked by it may operate on dbs_data with no users. Although
sysfs will cause the kobject_put() in cpufreq_governor_exit() to
block until governor_store() has returned, that situation may
lead to some unexpected results, depending on the implementation
of the ->store callback, and therefore it should be avoided.
To that end, modify governor_store() to check the dbs_data's
usage count before invoking the ->store() callback and return
an error if it is 0 at that point.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
-rw-r--r-- | drivers/cpufreq/cpufreq_governor.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c index 56dba71..65ed859 100644 --- a/drivers/cpufreq/cpufreq_governor.c +++ b/drivers/cpufreq/cpufreq_governor.c @@ -112,7 +112,7 @@ static ssize_t governor_store(struct kobject *kobj, struct attribute *attr, mutex_lock(&dbs_data->mutex); - if (gattr->store) + if (dbs_data->usage_count && gattr->store) ret = gattr->store(dbs_data, buf, count); mutex_unlock(&dbs_data->mutex); |