drm/radeon: fix regression in UMS CS ioctl

radeon_cs_parser_init is called by both the legacy UMS
CS ioctl and the KMS CS ioctl.  Protect KMS specific
pieces of the code by checking that rdev is not NULL.
Reported-by: Michael Burian <michael.burian@sbg.at>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/radeon_cs.c

@@ -147,6 +147,7 @@ static int radeon_cs_sync_rings(struct radeon_cs_parser *p)
 					   sync_to_ring, p->ring);
 }
 
+/* XXX: note that this is called from the legacy UMS CS ioctl as well */
 int radeon_cs_parser_init(struct radeon_cs_parser *p, void *data)
 {
 	struct drm_radeon_cs *cs = data;
@@ -245,22 +246,24 @@ int radeon_cs_parser_init(struct radeon_cs_parser *p, void *data)
 		}
 	}
 
-	if ((p->cs_flags & RADEON_CS_USE_VM) &&
-	    !p->rdev->vm_manager.enabled) {
-		DRM_ERROR("VM not active on asic!\n");
-		return -EINVAL;
-	}
-
-	/* we only support VM on SI+ */
-	if ((p->rdev->family >= CHIP_TAHITI) &&
-	    ((p->cs_flags & RADEON_CS_USE_VM) == 0)) {
-		DRM_ERROR("VM required on SI+!\n");
-		return -EINVAL;
-	}
+	/* these are KMS only */
+	if (p->rdev) {
+		if ((p->cs_flags & RADEON_CS_USE_VM) &&
+		    !p->rdev->vm_manager.enabled) {
+			DRM_ERROR("VM not active on asic!\n");
+			return -EINVAL;
+		}
 
-	if (radeon_cs_get_ring(p, ring, priority))
-		return -EINVAL;
+		/* we only support VM on SI+ */
+		if ((p->rdev->family >= CHIP_TAHITI) &&
+		    ((p->cs_flags & RADEON_CS_USE_VM) == 0)) {
+			DRM_ERROR("VM required on SI+!\n");
+			return -EINVAL;
+		}
 
+		if (radeon_cs_get_ring(p, ring, priority))
+			return -EINVAL;
+	}
 
 	/* deal with non-vm */
 	if ((p->chunk_ib_idx != -1) &&