backlight: grab ops_lock before testing bd->ops

commit d1d73578e053b981c3611e5a211534290d24a5eb upstream.

According to the comment describing ops_lock in the definition of struct
backlight_device and when comparing with other functions in backlight.c
the mutex must be hold when checking ops to be non-NULL.

Fixes a problem added by c835ee7f4154992e6 ("backlight: Add suspend/resume
support to the backlight core") in Jan 2009.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Richard Purdie <rpurdie@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
index 6615ac7fa60a6124e31257a2ce1b09cf871ed719..5e20e6ec17197649b54db2f3f5cda0557dfdfd52 100644 (file)
--- a/drivers/video/backlight/backlight.c
+++ b/drivers/video/backlight/backlight.c
@@ -196,12 +196,12 @@ static int backlight_suspend(struct device *dev, pm_message_t state)
 {
        struct backlight_device *bd = to_backlight_device(dev);
 
-       if (bd->ops->options & BL_CORE_SUSPENDRESUME) {
-               mutex_lock(&bd->ops_lock);
+       mutex_lock(&bd->ops_lock);
+       if (bd->ops && bd->ops->options & BL_CORE_SUSPENDRESUME) {
                bd->props.state |= BL_CORE_SUSPENDED;
                backlight_update_status(bd);
-               mutex_unlock(&bd->ops_lock);
        }
+       mutex_unlock(&bd->ops_lock);
 
        return 0;
 }
@@ -210,12 +210,12 @@ static int backlight_resume(struct device *dev)
 {
        struct backlight_device *bd = to_backlight_device(dev);
 
-       if (bd->ops->options & BL_CORE_SUSPENDRESUME) {
-               mutex_lock(&bd->ops_lock);
+       mutex_lock(&bd->ops_lock);
+       if (bd->ops && bd->ops->options & BL_CORE_SUSPENDRESUME) {
                bd->props.state &= ~BL_CORE_SUSPENDED;
                backlight_update_status(bd);
-               mutex_unlock(&bd->ops_lock);
        }
+       mutex_unlock(&bd->ops_lock);
 
        return 0;
 }