ui/virtio-gpu: add and use qemu_create_displaysurface_pixman

Add a the new qemu_create_displaysurface_pixman function, to create
a DisplaySurface backed by an existing pixman image.  In that case
there is no need to create a new pixman image pointing to the same
backing storage.  We can just use the existing image directly.

This does not only simplify things a bit, but most importantly it
gets the reference counting right, so the backing storage for the
pixman image wouldn't be released underneath us.

Use new function in virtio-gpu, where using it actually fixes
use-after-free crashes.

Cc: qemu-stable@nongnu.org
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-id: 1459499240-742-1-git-send-email-kraxel@redhat.com

1 files changed, 11 insertions, 0 deletions

diff --git a/ui/console.c b/ui/console.c
index 1fd4ea4d2e..bf385790b5 100644
--- a/ui/console.c
+++ b/ui/console.c
@@ -1292,6 +1292,17 @@ DisplaySurface *qemu_create_displaysurface_from(int width, int height,
     return surface;
 }
 
+DisplaySurface *qemu_create_displaysurface_pixman(pixman_image_t *image)
+{
+    DisplaySurface *surface = g_new0(DisplaySurface, 1);
+
+    trace_displaysurface_create_pixman(surface);
+    surface->format = pixman_image_get_format(image);
+    surface->image = pixman_image_ref(image);
+
+    return surface;
+}
+
 static void qemu_unmap_displaysurface_guestmem(pixman_image_t *image,
                                                void *unused)
 {