vhost-user-gpu: fix memory leak while calling 'vg_resource_unref' (CVE-2021-3544)

If the guest trigger following sequences, the attach_backing will be leaked:

vg_resource_create_2d
vg_resource_attach_backing
vg_resource_unref

This patch fix this by freeing 'res->iov' in vg_resource_destroy.

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")
Reviewed-by: default avatarPrasad J Pandit <pjp@fedoraproject.org>
Signed-off-by: default avatarLi Qiang <liq3ea@163.com>
Reviewed-by: Marc-André Lureau's avatarMarc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20210516030403.107723-5-liq3ea@163.com>
Signed-off-by: Gerd Hoffmann's avatarGerd Hoffmann <kraxel@redhat.com>

Upstream-Status: Backport
CVE: CVE-2021-3544
[vhost-user-gpu does not exist in the 4.2.0]
Signed-off-by: Armin Kuster <akuster@mvista.com>

Index: qemu-4.2.0/contrib/vhost-user-gpu/main.c
===================================================================
--- qemu-4.2.0.orig/contrib/vhost-user-gpu/main.c
+++ qemu-4.2.0/contrib/vhost-user-gpu/main.c
@@ -379,6 +379,7 @@ vg_resource_destroy(VuGpu *g,
     }
 
     vugbm_buffer_destroy(&res->buffer);
+    g_free(res->iov);
     pixman_image_unref(res->image);
     QTAILQ_REMOVE(&g->reslist, res, next);
     g_free(res);