Commit da096fe1 authored May 31, 2019 by Willem de Bruijn Committed by Greg Kroah-Hartman Jun 11, 2019

packet: unconditionally free po->rollover



[ Upstream commit afa0925c6fcc6a8f610e996ca09bc3215048033c ]

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: 57f015f5 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent be0343af

net/packet/af_packet.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -3017,8 +3017,8 @@ static int packet_release(struct socket *sock)

		synchronize_net();

		if (f) {
		kfree(po->rollover);
		if (f) {
		fanout_release_data(f);
		kfree(f);
		}