drm/radeon: check the alloc_workqueue return value

hulk inclusion
category: bugfix
bugzilla: 47877
CVE: CVE-2019-16230

-------------------------------------------------

check the alloc_workqueue return value in radeon_crtc_init()
to avoid null-ptr-deref.
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Reviewed-by: NHanjun Guo <guohanjun@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Reviewed-by: NXie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

drivers/gpu/drm/radeon/radeon_display.c

@@ -689,11 +689,16 @@ static void radeon_crtc_init(struct drm_device *dev, int index)
 	if (radeon_crtc == NULL)
 		return;
 
+	radeon_crtc->flip_queue = alloc_workqueue("radeon-crtc", WQ_HIGHPRI, 0);
+	if (!radeon_crtc->flip_queue) {
+		kfree(radeon_crtc);
+		return;
+	}
+
 	drm_crtc_init(dev, &radeon_crtc->base, &radeon_crtc_funcs);
 
 	drm_mode_crtc_set_gamma_size(&radeon_crtc->base, 256);
 	radeon_crtc->crtc_id = index;
-	radeon_crtc->flip_queue = alloc_workqueue("radeon-crtc", WQ_HIGHPRI, 0);
 	rdev->mode_info.crtcs[index] = radeon_crtc;
 
 	if (rdev->family >= CHIP_BONAIRE) {