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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>
This commit is contained in:
Manfred Schlaegl 2013-08-13 04:17:05 -07:00 committed by Bryan Wu
parent 8a6acd648c
commit c945cbcf45
1 changed files with 16 additions and 14 deletions
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30
drivers/leds/trigger/ledtrig-backlight.c
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@ -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;
}