Merge branch 'ptr_ring-fixes'

Michael S. Tsirkin says:

====================
ptr_ring fixes

This fixes a bunch of issues around ptr_ring use in net core.
One of these: "tap: fix use-after-free" is also needed on net,
but can't be backported cleanly.

I will post a net patch separately.

Lightly tested - Jason, could you pls confirm this
addresses the security issue you saw with ptr_ring?
Testing reports would be appreciated too.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
Tested-by: Jason Wang <jasowang@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>