[PATCH 08/13] drm/irq: Check for valid VBLANK before dereference

[Thierry Reding]

From: Thierry Reding <treding at nvidia.com>

When accessing the array of per-CRTC VBLANK structures we must always
check that the index into the array is valid before dereferencing to
avoid crashing.

Signed-off-by: Thierry Reding <treding at nvidia.com>
---
 drivers/gpu/drm/drm_irq.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index a24658162284..cb207e047505 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -1070,10 +1070,10 @@ void drm_vblank_put(struct drm_device *dev, int crtc)
 {
 	struct drm_vblank_crtc *vblank = &dev->vblank[crtc];
 
-	if (WARN_ON(atomic_read(&vblank->refcount) == 0))
+	if (WARN_ON(crtc >= dev->num_crtcs))
 		return;
 
-	if (WARN_ON(crtc >= dev->num_crtcs))
+	if (WARN_ON(atomic_read(&vblank->refcount) == 0))
 		return;
 
 	/* Last user schedules interrupt disable */
@@ -1356,6 +1356,9 @@ void drm_vblank_post_modeset(struct drm_device *dev, int crtc)
 	if (!dev->num_crtcs)
 		return;
 
+	if (WARN_ON(crtc >= dev->num_crtcs))
+		return;
+
 	if (vblank->inmodeset) {
 		spin_lock_irqsave(&dev->vbl_lock, irqflags);
 		dev->vblank_disable_allowed = true;
-- 
2.1.3