Merge branch 'net-handshake-fixes'

Chuck Lever says:

====================
Bug fixes for net/handshake

Please consider these for merge via net-next.

Paolo observed that there is a possible leak of sock->file. I
haven't looked into that yet, but it seems to be separate from
the fixes in this series, so no need to hold these up.

Changes since v2:
- Address Paolo comment regarding handshake_dup()

Changes since v1:
- Rework "Fix handshake_dup() ref counting"
- Unpin sock->file when a handshake is cancelled
====================

Signed-off-by: David S. Miller <davem@davemloft.net>