vhost-user-gpu: fix memory leak in 'virgl_cmd_resource_unref' (CVE-2021-3544)

The 'res->iov' will be leaked if the guest trigger following sequences:

virgl_cmd_create_resource_2d
virgl_resource_attach_backing
virgl_cmd_resource_unref

This patch fixes this.

Fixes: CVE-2021-3544
Reported-by: default avatarLi Qiang <liq3ea@163.com>
virtio-gpu fix: 5e8e3c4c

("virtio-gpu: fix resource leak
in virgl_cmd_resource_unref"
Signed-off-by: default avatarLi Qiang <liq3ea@163.com>
Reviewed-by: Marc-André Lureau's avatarMarc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20210516030403.107723-6-liq3ea@163.com>
Signed-off-by: Gerd Hoffmann's avatarGerd Hoffmann <kraxel@redhat.com>

Upstream-Status: Backport
CVE: CVE-2021-3544
Signed-off-by: Armin Kuster <akuster@mvista.com>

Index: qemu-4.2.0/contrib/vhost-user-gpu/virgl.c
===================================================================
--- qemu-4.2.0.orig/contrib/vhost-user-gpu/virgl.c
+++ qemu-4.2.0/contrib/vhost-user-gpu/virgl.c
@@ -105,9 +105,16 @@ virgl_cmd_resource_unref(VuGpu *g,
                          struct virtio_gpu_ctrl_command *cmd)
 {
     struct virtio_gpu_resource_unref unref;
+    struct iovec *res_iovs = NULL;
+    int num_iovs = 0;
 
     VUGPU_FILL_CMD(unref);
 
+    virgl_renderer_resource_detach_iov(unref.resource_id,
+            &res_iovs,
+            &num_iovs);
+    g_free(res_iovs);
+
     virgl_renderer_resource_unref(unref.resource_id);
 }