packet: unconditionally free po->rollover
authorWillem de Bruijn <willemb@google.com>
Fri, 31 May 2019 16:37:23 +0000 (12:37 -0400)
committerDavid S. Miller <davem@davemloft.net>
Mon, 3 Jun 2019 01:10:14 +0000 (18:10 -0700)
commitafa0925c6fcc6a8f610e996ca09bc3215048033c
tree626dcaed42ebd07593d937544ee61346102ea05c
parent8c268598192df9a07ca967f6a8d5f12c3c1b3888
packet: unconditionally free po->rollover

Rollover used to use a complex RCU mechanism for assignment, which had
a race condition. The below patch fixed the bug and greatly simplified
the logic.

The feature depends on fanout, but the state is private to the socket.
Fanout_release returns f only when the last member leaves and the
fanout struct is to be freed.

Destroy rollover unconditionally, regardless of fanout state.

Fixes: 57f015f5eccf2 ("packet: fix crash in fanout_demux_rollover()")
Reported-by: syzbot <syzkaller@googlegroups.com>
Diagnosed-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
net/packet/af_packet.c