| Message ID | 20191018105815.5714-1-sudeep.holla@arm.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] cpufreq: cancel any pending policy update work scheduled before freeing | expand |
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index e93cba29fbb2..8ad9c2859841 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -1279,6 +1279,8 @@ static void cpufreq_policy_free(struct cpufreq_policy *policy) } dev_pm_qos_remove_request(policy->min_freq_req); + /* cancel any pending policy->update work before freeing the policy */ + cancel_work_sync(&policy->update); kfree(policy->min_freq_req); cpufreq_policy_put_kobj(policy);
Schedules policy update work may end up racing with the freeing of the policy and unregistering the driver. One possible race is as below where the cpufreq_driver is unregistered but the scheduled work gets executed at later stage when cpufreq_driver is NULL(i.e. after freeing the policy and driver) Unable to handle kernel NULL pointer dereference at virtual address 0000001c pgd = (ptrval) [0000001c] *pgd=80000080204003, *pmd=00000000 Internal error: Oops: 206 [#1] SMP THUMB2 Modules linked in: CPU: 0 PID: 34 Comm: kworker/0:1 Not tainted 5.4.0-rc3-00006-g67f5a8081a4b #86 Hardware name: ARM-Versatile Express Workqueue: events handle_update PC is at cpufreq_set_policy+0x58/0x228 LR is at dev_pm_qos_read_value+0x77/0xac Control: 70c5387d Table: 80203000 DAC: fffffffd Process kworker/0:1 (pid: 34, stack limit = 0x(ptrval)) (cpufreq_set_policy) from (refresh_frequency_limits.part.24+0x37/0x48) (refresh_frequency_limits.part.24) from (handle_update+0x2f/0x38) (handle_update) from (process_one_work+0x16d/0x3cc) (process_one_work) from (worker_thread+0xff/0x414) (worker_thread) from (kthread+0xff/0x100) (kthread) from (ret_from_fork+0x11/0x28) Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> Cc: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com> --- drivers/cpufreq/cpufreq.c | 2 ++ 1 file changed, 2 insertions(+) v1->v2: - Dropped check for work_pending as it can still be racy - Changed from flush_work to cancel_work_sync -- 2.17.1