From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Tue, 7 Apr 2009 02:40:20 +0000 (-0700)
Subject: drm/i915: Check for dev->primary->master before dereference.
X-Git-Tag: v2.6.29.2~83
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=89051add552d18e1f212a5111e7e8a059a67ae10;p=thirdparty%2Fkernel%2Fstable.git

drm/i915: Check for dev->primary->master before dereference.

upstream commit: 98787c057fdefdce6230ff46f2c1105835005a4c

I've hit the occasional oops inside i915_wait_ring() with an indication of
a NULL derefence of dev->primary->master.  Adding a NULL check is
consistent with the other potential users of dev->primary->master.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
---

diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 6d21b9e48b89a..908d24e4a23e6 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -41,7 +41,6 @@
 int i915_wait_ring(struct drm_device * dev, int n, const char *caller)
 {
 	drm_i915_private_t *dev_priv = dev->dev_private;
-	struct drm_i915_master_private *master_priv = dev->primary->master->driver_priv;
 	drm_i915_ring_buffer_t *ring = &(dev_priv->ring);
 	u32 acthd_reg = IS_I965G(dev) ? ACTHD_I965 : ACTHD;
 	u32 last_acthd = I915_READ(acthd_reg);
@@ -58,8 +57,12 @@ int i915_wait_ring(struct drm_device * dev, int n, const char *caller)
 		if (ring->space >= n)
 			return 0;
 
-		if (master_priv->sarea_priv)
-			master_priv->sarea_priv->perf_boxes |= I915_BOX_WAIT;
+		if (dev->primary->master) {
+			struct drm_i915_master_private *master_priv = dev->primary->master->driver_priv;
+			if (master_priv->sarea_priv)
+				master_priv->sarea_priv->perf_boxes |= I915_BOX_WAIT;
+		}
+
 
 		if (ring->head != last_head)
 			i = 0;