vsock/virtio: Initialization of the dangling pointer occurring in vsk->trans

During loopback communication, a dangling pointer can be created in
vsk->trans, potentially leading to a Use-After-Free condition.  This
issue is resolved by initializing vsk->trans to NULL.

Cc: stable <stable@kernel.org>
Fixes: 06a8fc78 ("VSOCK: Introduce virtio_vsock_common.ko")
Signed-off-by: Hyunwoo Kim <v4bel@theori.io>
Signed-off-by: Wongi Lee <qwerty@theori.io>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Message-Id: <2024102245-strive-crib-c8d3@gregkh>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>