Input: pwm-beeper - fix race when suspending

Usually userspace sends SND_BELL and SND_TONE events, and by the time
pwm_beeper_suspend() runs userpsace is already frozen, but theoretically
in-kernel users may send these events too, and that may cause
pwm_beeper_event() scheduling another work after we canceled it.

Let's introduce a "suspended" flag and check it in pwm_beeper_event() to
avoid this race.

Reviewed-by: Thierry Reding <thierry.reding@gmail.com>
Tested-by: David Lechner <david@lechnology.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

diff --git a/drivers/input/misc/pwm-beeper.c b/drivers/input/misc/pwm-beeper.c
index 58a60b4..9d7987d 100644 (file)
--- a/drivers/input/misc/pwm-beeper.c
+++ b/drivers/input/misc/pwm-beeper.c
@@ -27,6 +27,7 @@ struct pwm_beeper {
        struct pwm_device *pwm;
        struct work_struct work;
        unsigned long period;
+       bool suspended;
 };
 
 #define HZ_TO_NANOSECONDS(x) (1000000000UL/(x))
@@ -73,7 +74,8 @@ static int pwm_beeper_event(struct input_dev *input,
        else
                beeper->period = HZ_TO_NANOSECONDS(value);
 
-       schedule_work(&beeper->work);
+       if (!beeper->suspended)
+               schedule_work(&beeper->work);
 
        return 0;
 }
@@ -154,6 +156,15 @@ static int __maybe_unused pwm_beeper_suspend(struct device *dev)
 {
        struct pwm_beeper *beeper = dev_get_drvdata(dev);
 
+       /*
+        * Spinlock is taken here is not to protect write to
+        * beeper->suspended, but to ensure that pwm_beeper_event
+        * does not re-submit work once flag is set.
+        */
+       spin_lock_irq(&beeper->input->event_lock);
+       beeper->suspended = true;
+       spin_unlock_irq(&beeper->input->event_lock);
+
        pwm_beeper_stop(beeper);
 
        return 0;
@@ -163,8 +174,12 @@ static int __maybe_unused pwm_beeper_resume(struct device *dev)
 {
        struct pwm_beeper *beeper = dev_get_drvdata(dev);
 
-       if (beeper->period)
-               __pwm_beeper_set(beeper);
+       spin_lock_irq(&beeper->input->event_lock);
+       beeper->suspended = false;
+       spin_unlock_irq(&beeper->input->event_lock);
+
+       /* Let worker figure out if we should resume beeping */
+       schedule_work(&beeper->work);
 
        return 0;
 }