Patch "drm: avoid uninitialized timestamp use in wait_vblank" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

drm: avoid uninitialized timestamp use in wait_vblank

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
drm-avoid-uninitialized-timestamp-use-in-wait_vblank.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Arnd Bergmann <[email protected]>
Date: Tue, 18 Oct 2016 00:13:39 +0200
Subject: drm: avoid uninitialized timestamp use in wait_vblank

From: Arnd Bergmann <[email protected]>

commit cff52e5fc4cfc978b7df898dc14a0492c7ef0ae8 upstream.

gcc warns about the timestamp in drm_wait_vblank being possibly used without an initialization:

drivers/gpu/drm/drm_irq.c: In function 'drm_crtc_send_vblank_event':
drivers/gpu/drm/drm_irq.c:992:24: error: 'now.tv_usec' may be used uninitialized in this function [-Werror=maybe-uninitialized] drivers/gpu/drm/drm_irq.c:1069:17: note: 'now.tv_usec' was declared here
drivers/gpu/drm/drm_irq.c:991:23: error: 'now.tv_sec' may be used uninitialized in this function [-Werror=maybe-uninitialized]

This can happen if drm_vblank_count_and_time() returns 0 in its error path. To sanitize the error case, I'm changing that function to return a zero timestamp when it fails.

---
 drivers/gpu/drm/drm_irq.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

@@ -952,8 +952,10 @@ static u32 drm_vblank_count_and_time(str
 	u32 vblank_count;
 	unsigned int seq;
 
-	if (WARN_ON(pipe >= dev->num_crtcs))
+	if (WARN_ON(pipe >= dev->num_crtcs)) {
+		*vblanktime = (struct timeval) { 0 };
 		return 0;
+	}
 
 	do {
 		seq = read_seqbegin(&vblank->seqlock);

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/drm-avoid-uninitialized-timestamp-use-in-wait_vblank.patch queue-4.9/bus-vexpress-config-fix-device-reference-leak.patch