From: Willem de Bruijn willemb@google.com
[ 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@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 --- 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 @@ -3016,8 +3016,8 @@ static int packet_release(struct socket
synchronize_net();
+ kfree(po->rollover); if (f) { - kfree(po->rollover); fanout_release_data(f); kfree(f); }