From e4ffdf9ead59a909f2824a4270356909d6d64380 Mon Sep 17 00:00:00 2001 From: Willem de Bruijn Date: Thu, 14 Sep 2017 17:14:41 -0400 Subject: packet: hold bind lock when rebinding to fanout hook [ Upstream commit 008ba2a13f2d04c947adc536d19debb8fe66f110 ] Packet socket bind operations must hold the po->bind_lock. This keeps po->running consistent with whether the socket is actually on a ptype list to receive packets. fanout_add unbinds a socket and its packet_rcv/tpacket_rcv call, then binds the fanout object to receive through packet_rcv_fanout. Make it hold the po->bind_lock when testing po->running and rebinding. Else, it can race with other rebind operations, such as that in packet_set_ring from packet_rcv to tpacket_rcv. Concurrent updates can result in a socket being added to a fanout group twice, causing use-after-free KASAN bug reports, among others. Reported independently by both trinity and syzkaller. Verified that the syzkaller reproducer passes after this patch. Fixes: dc99f600698d ("packet: Add fanout support.") Reported-by: nixioaming Signed-off-by: Willem de Bruijn Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/packet/af_packet.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) (limited to 'net') diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 7effa07c4491..9f1820e3c8b1 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -1429,9 +1429,6 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags) return -EINVAL; } - if (!po->running) - return -EINVAL; - if (po->fanout) return -EALREADY; @@ -1469,7 +1466,10 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags) list_add(&match->list, &fanout_list); } err = -EINVAL; - if (match->type == type && + + spin_lock(&po->bind_lock); + if (po->running && + match->type == type && match->prot_hook.type == po->prot_hook.type && match->prot_hook.dev == po->prot_hook.dev) { err = -ENOSPC; @@ -1481,6 +1481,13 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags) err = 0; } } + spin_unlock(&po->bind_lock); + + if (err && !atomic_read(&match->sk_ref)) { + list_del(&match->list); + kfree(match); + } + out: mutex_unlock(&fanout_mutex); return err; -- cgit v1.2.3