[PATCH 4.19 12/51] packet: unconditionally free po->rollover

From: Greg Kroah-Hartman
Date: Sun Jun 09 2019 - 12:51:58 EST

From: Willem de Bruijn <willemb@xxxxxxxxxx>

[ 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: 57f015f5eccf2 ("packet: fix crash in fanout_demux_rollover()")
Reported-by: syzbot <syzkaller@xxxxxxxxxxxxxxxx>
Diagnosed-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Signed-off-by: Willem de Bruijn <willemb@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
net/packet/af_packet.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -3017,8 +3017,8 @@ static int packet_release(struct socket


+ kfree(po->rollover);
if (f) {
- kfree(po->rollover);