From c945cbcf453cb72dc2287fc4f7b63314f173b313 Mon Sep 17 00:00:00 2001 From: Manfred Schlaegl <manfred.schlaegl@gmx.at> Date: Tue, 13 Aug 2013 04:17:05 -0700 Subject: 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> --- drivers/leds/trigger/ledtrig-backlight.c | 30 ++++++++++++++++-------------- 1 file changed, 16 insertions(+), 14 deletions(-) (limited to 'drivers/leds') diff --git a/drivers/leds/trigger/ledtrig-backlight.c b/drivers/leds/trigger/ledtrig-backlight.c index 3c9c88a07eb8..47e55aa9eefa 100644 --- a/drivers/leds/trigger/ledtrig-backlight.c +++ b/drivers/leds/trigger/ledtrig-backlight.c @@ -36,26 +36,28 @@ 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; - switch (event) { - case FB_EVENT_BLANK: - if (new_status == n->old_status) - break; + /* If we aren't interested in this event, skip it immediately ... */ + if (event != FB_EVENT_BLANK) + return 0; - if ((n->old_status == UNBLANK) ^ n->invert) { - n->brightness = led->brightness; - __led_set_brightness(led, LED_OFF); - } else { - __led_set_brightness(led, n->brightness); - } + blank = fb_event->data; + new_status = *blank ? BLANK : UNBLANK; - n->old_status = new_status; + if (new_status == n->old_status) + return 0; - break; + if ((n->old_status == UNBLANK) ^ n->invert) { + n->brightness = led->brightness; + __led_set_brightness(led, LED_OFF); + } else { + __led_set_brightness(led, n->brightness); } + n->old_status = new_status; + return 0; } -- cgit v1.2.3