4.4-stable review patch. If anyone has any objections, please let me know.
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From: Tao Wang kevin.wangtao@hisilicon.com
commit c7d1f119c48f64bebf0fa1e326af577c6152fe30 upstream.
If the policy limits are updated via cpufreq_update_policy() and subsequently via sysfs, the limits stored in user_policy may be set incorrectly.
For example, if both min and max are set via sysfs to the maximum available frequency, user_policy.min and user_policy.max will also be the maximum. If a policy notifier triggered by cpufreq_update_policy() lowers both the min and the max at this point, that change is not reflected by the user_policy limits, so if the max is updated again via sysfs to the same lower value, then user_policy.max will be lower than user_policy.min which shouldn't happen. In particular, if one of the policy CPUs is then taken offline and back online, cpufreq_set_policy() will fail for it due to a failing limits check.
To prevent that from happening, initialize the min and max fields of the new_policy object to the ones stored in user_policy that were previously set via sysfs.
Signed-off-by: Kevin Wangtao kevin.wangtao@hisilicon.com Acked-by: Viresh Kumar viresh.kumar@linaro.org [ rjw: Subject & changelog ] Cc: All applicable stable@vger.kernel.org Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/cpufreq/cpufreq.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -603,6 +603,8 @@ static ssize_t store_##file_name \ struct cpufreq_policy new_policy; \ \ memcpy(&new_policy, policy, sizeof(*policy)); \ + new_policy.min = policy->user_policy.min; \ + new_policy.max = policy->user_policy.max; \ \ ret = sscanf(buf, "%u", &new_policy.object); \ if (ret != 1) \