From 0575034b1a1317bed60be47e6fbb014f81d7fbc2 Mon Sep 17 00:00:00 2001
From: Vivek Kasireddy <vivek.kasireddy@intel.com>
Date: Thu, 4 Nov 2021 14:42:49 -0700
Subject: drm/virtio: Fix NULL dereference error in virtio_gpu_poll
Git-commit: d89c0c8322ecdc9a2ec84b959b6f766be082da76
Patch-mainline: v5.16-rc1
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225

When virgl is not enabled, vfpriv pointer would not be allocated.
Therefore, check for a valid value before dereferencing.

Reported-by: Christian Zigotzky <chzigotzky@xenosoft.de>
Cc: Gurchetan Singh <gurchetansingh@chromium.org>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
Tested-by: Christian Zigotzky <chzigotzky@xenosoft.de>
Link: http://patchwork.freedesktop.org/patch/msgid/20211104214249.1802789-1-vivek.kasireddy@intel.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 drivers/gpu/drm/virtio/virtgpu_drv.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.c b/drivers/gpu/drm/virtio/virtgpu_drv.c
index 749db18dcfa2..d86e1ad4a972 100644
--- a/drivers/gpu/drm/virtio/virtgpu_drv.c
+++ b/drivers/gpu/drm/virtio/virtgpu_drv.c
@@ -163,10 +163,11 @@ static __poll_t virtio_gpu_poll(struct file *filp,
 	struct drm_file *drm_file = filp->private_data;
 	struct virtio_gpu_fpriv *vfpriv = drm_file->driver_priv;
 	struct drm_device *dev = drm_file->minor->dev;
+	struct virtio_gpu_device *vgdev = dev->dev_private;
 	struct drm_pending_event *e = NULL;
 	__poll_t mask = 0;
 
-	if (!vfpriv->ring_idx_mask)
+	if (!vgdev->has_virgl_3d || !vfpriv || !vfpriv->ring_idx_mask)
 		return drm_poll(filp, wait);
 
 	poll_wait(filp, &drm_file->event_wait, wait);
-- 
2.38.1