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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: 57f015f5ec ("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>
This commit is contained in:
Willem de Bruijn 2019-05-31 12:37:23 -04:00 committed by David S. Miller
parent 8c26859819
commit afa0925c6f
1 changed files with 1 additions and 1 deletions
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2
net/packet/af_packet.c
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@ -3014,8 +3014,8 @@ static int packet_release(struct socket *sock)
synchronize_net();
kfree(po->rollover);
if (f) {
kfree(po->rollover);
fanout_release_data(f);
kfree(f);
}