[patch 018/100] drm/i915: Check for dev->primary->master before dereference.

Chris Wright
2009-04-23T07:35:27Z

[-- Attachment #1: drm-i915-check-for-dev-primary-master-before-dereference.patch --]
[-- Type: text/plain, Size: 1567 bytes --]

-stable review patch. If anyone has any objections, please let us know.
---------------------

From: Chris Wilson <chris@chris-wilson.co.uk>

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>
---
drivers/gpu/drm/i915/i915_dma.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)

--- 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 * d
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;