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

[Thierry Reding <thierry.reding@gmail.com>]

From: Thierry Reding <treding@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@nvidia.com>
---
 drivers/gpu/drm/drm_irq.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index 5c666c780fe9..a957b9618e85 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -1110,10 +1110,10 @@ 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 */
@@ -1158,6 +1158,9 @@ void drm_wait_one_vblank(struct drm_device *dev, int crtc)
 	int ret;
 	u32 last;
 
+	if (WARN_ON(crtc >= dev->num_crtcs))
+		return;
+
 	ret = drm_vblank_get(dev, crtc);
 	if (WARN(ret, "vblank not available on crtc %i, ret=%i\n", crtc, ret))
 		return;
@@ -1428,6 +1431,9 @@ 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;
-- 
2.4.5

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