In the Linux kernel, the following vulnerability has been resolved:
xen-netback: Zero out sring pointers on unmap
If xenvif_map_frontend_data_rings() fails when a ring is already mapped,
it unmaps them via xenvif_unmap_frontend_data_rings() which keeps the
ring pointers unchanged. xenvif_connect_data()'s cleanup path calls
xenvif_disconnect_queue() which in turn calls
xenvif_unmap_frontend_data_rings() again, which will attempt to unmap the
pointers a second time.
Zero out the ring pointers after they are unmapped to avoid this issue.
This is XSA-532
