[PATCH 5.10 171/545] virtio-gpu: fix a missing check to avoid NULL dereference

[Greg Kroah-Hartman]

From: Xiaomeng Tong <xiam0nd.tong@xxxxxxxxx>

[ Upstream commit bd63f11f4c3c46afec07d821f74736161ff6e526 ]

'cache_ent' could be set NULL inside virtio_gpu_cmd_get_capset()
and it will lead to a NULL dereference by a lately use of it
(i.e., ptr = cache_ent->caps_cache). Fix it with a NULL check.

Fixes: 62fb7a5e10962 ("virtio-gpu: add 3d/virgl support")
Signed-off-by: Xiaomeng Tong <xiam0nd.tong@xxxxxxxxx>
Reviewed-by: Chia-I Wu <olvaffe@xxxxxxxxx>
Link: http://patchwork.freedesktop.org/patch/msgid/20220327050945.1614-1-xiam0nd.tong@xxxxxxxxx

[ kraxel: minor codestyle fixup ]

Signed-off-by: Gerd Hoffmann <kraxel@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/gpu/drm/virtio/virtgpu_ioctl.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
index c8da7adc6b30..33b8ebab178a 100644
--- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
+++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
@@ -470,8 +470,10 @@ static int virtio_gpu_get_caps_ioctl(struct drm_device *dev,
 	spin_unlock(&vgdev->display_info_lock);
 
 	/* not in cache - need to talk to hw */
-	virtio_gpu_cmd_get_capset(vgdev, found_valid, args->cap_set_ver,
-				  &cache_ent);
+	ret = virtio_gpu_cmd_get_capset(vgdev, found_valid, args->cap_set_ver,
+					&cache_ent);
+	if (ret)
+		return ret;
 	virtio_gpu_notify(vgdev);
 
 copy_exit:
-- 
2.35.1