[PATCH V7 1/6] cpufreq: Don't allow updating inactive policies from sysfs
From: Viresh Kumar <viresh.kumar@linaro.org>
Date: 2015-06-08 12:55:53
Subsystem:
cpu frequency scaling framework, the rest · Maintainers:
"Rafael J. Wysocki", Viresh Kumar, Linus Torvalds
Later commits would change the way policies are managed today. Policies wouldn't be freed on cpu hotplug (currently they aren't freed only for suspend), and while the CPU is offline, the sysfs cpufreq files would still be present. User may accidentally try to update the sysfs files in following directory: '/sys/devices/system/cpu/cpuX/cpufreq/'. And that would result in undefined behavior as policy wouldn't be active then. Apart from updating the store() routine, we also update __cpufreq_get() which can call cpufreq_out_of_sync(). The later routine tries to update policy->cur and starts notifying kernel about it. Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> --- drivers/cpufreq/cpufreq.c | 11 +++++++++++ 1 file changed, 11 insertions(+)
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 5d780ff5a10a..7eeff892c0a6 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c@@ -875,11 +875,18 @@ static ssize_t store(struct kobject *kobj, struct attribute *attr, down_write(&policy->rwsem); + /* Updating inactive policies is invalid, so avoid doing that. */ + if (unlikely(policy_is_inactive(policy))) { + ret = -EPERM; + goto unlock_policy_rwsem; + } + if (fattr->store) ret = fattr->store(policy, buf, count); else ret = -EIO; +unlock_policy_rwsem: up_write(&policy->rwsem); up_read(&cpufreq_rwsem);
@@ -1610,6 +1617,10 @@ static unsigned int __cpufreq_get(struct cpufreq_policy *policy) ret_freq = cpufreq_driver->get(policy->cpu); + /* Updating inactive policies is invalid, so avoid doing that. */ + if (unlikely(policy_is_inactive(policy))) + return ret_freq; + if (ret_freq && policy->cur && !(cpufreq_driver->flags & CPUFREQ_CONST_LOOPS)) { /* verify no discrepancy between actual and
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2.4.0