Commit c945cbcf authored Aug 13, 2013 by Manfred Schlaegl Committed by Bryan Wu Aug 26, 2013

leds: trigger: ledtrig-backlight: Fix invalid memory access in fb_event notification callback



fb_notifier_callback is called on any event fired by
fb_notifier_call_chain. Events may, or may not contain some data
(fb_event.data). In case of FB_EVENT_BLANK fb_event.data contains a
pointer to an integer holdingthe blank state. The Problem is, that in
ledtrig-backlight.c - fb_notifier_callback the pointer to blank state
is dereferenced BEFORE the event-type is checked.

Obviously this leads to problems with other events than FB_EVENT_BLANK,
where fb_event.data is undefined or NULL. It seems, that this problem
existed ever since the driver was added.

Like in drivers/video/backlight/backlight.c line 43 I would suggest to
return immediately on events other than FB_EVENT_BLANK.

Signed-off-by: Manfred Schlaegl <manfred.schlaegl@gmx.at>
Signed-off-by: Bryan Wu <cooloney@gmail.com>

parent 8a6acd64

drivers/leds/trigger/ledtrig-backlight.c

+16 −14

Original line number	Diff line number	Diff line
		@@ -36,13 +36,18 @@ static int fb_notifier_callback(struct notifier_block *p,
		struct bl_trig_notifier, notifier);
		struct led_classdev *led = n->led;
		struct fb_event *fb_event = data;
		int *blank = fb_event->data;
		int new_status = *blank ? BLANK : UNBLANK;
		int *blank;
		int new_status;

		/* If we aren't interested in this event, skip it immediately ... */
		if (event != FB_EVENT_BLANK)
		return 0;

		blank = fb_event->data;
		new_status = *blank ? BLANK : UNBLANK;

		switch (event) {
		case FB_EVENT_BLANK:
		if (new_status == n->old_status)
		break;
		return 0;

		if ((n->old_status == UNBLANK) ^ n->invert) {
		n->brightness = led->brightness;
		@@ -53,9 +58,6 @@ static int fb_notifier_callback(struct notifier_block *p,

		n->old_status = new_status;

		break;
		}

		return 0;
		}