Re: [PATCH] leds: ledtrig-timer trigger_data allocation fix

From: Andrew Morton
Date: Tue Apr 17 2012 - 19:12:40 EST

On Tue, 17 Apr 2012 17:05:11 -0600
Shuah Khan <shuahkhan@xxxxxxxxx> wrote:

> ledtrig-timer doesn't allocate memory for trigger_data and assigns
> (void *)1 to save state. Fixed it to allocate int instead. Please
> note that non-null trigger_data is used to key off of to do proper
> cleanup in deactivation routine and not used during the life of the
> trigger itself.

In that case, overloading the value of ->trigger_data in this fashion
is inappropriate and a new field should be added to led_classdev for
this purpose.

> - led_cdev->trigger_data = (void *)1;
> + led_cdev->trigger_data = kzalloc(sizeof(int), GFP_KERNEL);

But that's better than what we have now.

It does require a comment though:

--- a/drivers/leds/ledtrig-timer.c~leds-ledtrig-timer-trigger_data-allocation-fix-fix
+++ a/drivers/leds/ledtrig-timer.c
@@ -89,6 +89,11 @@ static void timer_trig_activate(struct l
led_blink_set(led_cdev, &led_cdev->blink_delay_on,

+ /*
+ * Place a dummy allocation at ->trigger_data so that
+ * timer_trig_deactivate() cleans up correctly. This data is never
+ * actually used.
+ */
led_cdev->trigger_data = kzalloc(sizeof(int), GFP_KERNEL);
if (!led_cdev->trigger_data)
goto err_out_delayoff;

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