From: Philippe Mathieu-Daudé <f4bug@amsat.org>

If the 'i8042' property is not set, mouse events handled by
vmmouse_mouse_event() end calling i8042_isa_mouse_fake_event()
with a NULL argument, resulting in ps2_mouse_fake_event() being
called with invalid PS2MouseState pointer. Fix by requiring
the 'i8042' property to be always set:

  $ qemu-system-x86_64 -device vmmouse
  qemu-system-x86_64: -device vmmouse: 'i8042' link is not set

Fixes: 91c9e09147b ("vmmouse: convert to qdev")
Reported-by: Calvin Buckley <calvin@cmpct.info>
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/752
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20211201223253.36080-1-f4bug@amsat.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 hw/i386/vmmouse.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/hw/i386/vmmouse.c b/hw/i386/vmmouse.c
index 3d66368286..a56c185f15 100644
--- a/hw/i386/vmmouse.c
+++ b/hw/i386/vmmouse.c
@@ -286,6 +286,10 @@ static void vmmouse_realizefn(DeviceState *dev, Error **errp)
 
     DPRINTF("vmmouse_init\n");
 
+    if (!s->i8042) {
+        error_setg(errp, "'i8042' link is not set");
+        return;
+    }
     if (!object_resolve_path_type("", TYPE_VMPORT, NULL)) {
         error_setg(errp, "vmmouse needs a machine with vmport");
         return;
-- 
2.33.1