CVE-2021-46967

In the Linux kernel, the following vulnerability has been resolved:
vhost-vdpa: fix vm_flags for virtqueue doorbell mapping The virtqueue
doorbell is usually implemented via registeres but we don’t provide the
necessary vma->flags like VM_PFNMAP. This may cause several issues e.g when
userspace tries to map the doorbell via vhost IOTLB, kernel may panic due
to the page is not backed by page structure. This patch fixes this by
setting the necessary vm_flags. With this patch, try to map doorbell via
IOTLB will fail with bad address.