drm/i915: Fix use-before-null-check in i915_irq_emit().

This could be triggered by a client asking to emit an irq when the device
wasn't initialized.

Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Dave Airlie <airlied@linux.ie>

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 548ff2c66431..87b6b603469e 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -383,12 +383,13 @@ int i915_irq_emit(struct drm_device *dev, void *data,
         drm_i915_irq_emit_t *emit = data;
         int result;
 
-        RING_LOCK_TEST_WITH_RETURN(dev, file_priv);
-
         if (!dev_priv) {
                 DRM_ERROR("called with no initialization\n");
                 return -EINVAL;
         }
+
+        RING_LOCK_TEST_WITH_RETURN(dev, file_priv);
+
         mutex_lock(&dev->struct_mutex);
         result = i915_emit_irq(dev);
         mutex_unlock(&dev->struct_mutex);