Patch "drm/nouveau/tmr: fix corruption of the pending list when rescheduling an alarm" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

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

    drm/nouveau/tmr: fix corruption of the pending list when rescheduling an alarm

to the 4.4-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-nouveau-tmr-fix-corruption-of-the-pending-list-when-rescheduling-an-alarm.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 9fc64667ee48c9a25e7dca1a6bcb6906fec5bcc5 Mon Sep 17 00:00:00 2001
From: Ben Skeggs <bskeggs@redhat.com>
Date: Thu, 11 May 2017 17:03:05 +1000
Subject: drm/nouveau/tmr: fix corruption of the pending list when rescheduling an alarm

From: Ben Skeggs <bskeggs@redhat.com>

commit 9fc64667ee48c9a25e7dca1a6bcb6906fec5bcc5 upstream.

At least therm/fantog "attempts" to work around this issue, which could
lead to corruption of the pending alarm list.

Fix it properly by not updating the timestamp without the lock held, or
trying to add an already pending alarm to the pending alarm list....

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/gpu/drm/nouveau/nvkm/subdev/timer/base.c |   17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

--- a/drivers/gpu/drm/nouveau/nvkm/subdev/timer/base.c
+++ b/drivers/gpu/drm/nouveau/nvkm/subdev/timer/base.c
@@ -65,14 +65,17 @@ nvkm_timer_alarm(struct nvkm_timer *tmr,
 	struct nvkm_alarm *list;
 	unsigned long flags;
 
-	alarm->timestamp = nvkm_timer_read(tmr) + nsec;
-
-	/* append new alarm to list, in soonest-alarm-first order */
+	/* Remove alarm from pending list.
+	 *
+	 * This both protects against the corruption of the list,
+	 * and implements alarm rescheduling/cancellation.
+	 */
 	spin_lock_irqsave(&tmr->lock, flags);
-	if (!nsec) {
-		if (!list_empty(&alarm->head))
-			list_del(&alarm->head);
-	} else {
+	list_del_init(&alarm->head);
+
+	if (nsec) {
+		/* Insert into pending list, ordered earliest to latest. */
+		alarm->timestamp = nvkm_timer_read(tmr) + nsec;
 		list_for_each_entry(list, &tmr->alarms, head) {
 			if (list->timestamp > alarm->timestamp)
 				break;


Patches currently in stable-queue which might be from bskeggs@redhat.com are

queue-4.4/drm-nouveau-tmr-ack-interrupt-before-processing-alarms.patch
queue-4.4/drm-nouveau-tmr-fix-corruption-of-the-pending-list-when-rescheduling-an-alarm.patch
queue-4.4/drm-nouveau-tmr-avoid-processing-completed-alarms-when-adding-a-new-one.patch
queue-4.4/drm-nouveau-mmu-nv4a-use-nv04-mmu-rather-than-the-nv44-one.patch
queue-4.4/drm-nouveau-therm-remove-ineffective-workarounds-for-alarm-bugs.patch
queue-4.4/drm-nouveau-tmr-handle-races-with-hw-when-updating-the-next-alarm-time.patch