From d949cfedbcbab4e91590576cbace2671924ad69c Mon Sep 17 00:00:00 2001 From: LUU Duc Canh Date: Wed, 26 Sep 2018 22:28:52 +0200 Subject: tipc: ignore STATE_MSG on wrong link session The initial session number when a link is created is based on a random value, taken from struct tipc_net->random. It is then incremented for each link reset to avoid mixing protocol messages from different link sessions. However, when a bearer is reset all its links are deleted, and will later be re-created using the same random value as the first time. This means that if the link never went down between creation and deletion we will still sometimes have two subsequent sessions with the same session number. In virtual environments with potentially long transmission times this has turned out to be a real problem. We now fix this by randomizing the session number each time a link is created. With a session number size of 16 bits this gives a risk of session collision of 1/64k. To reduce this further, we also introduce a sanity check on the very first STATE message arriving at a link. If this has an acknowledge value differing from 0, which is logically impossible, we ignore the message. The final risk for session collision is hence reduced to 1/4G, which should be sufficient. Signed-off-by: LUU Duc Canh Signed-off-by: Jon Maloy Signed-off-by: David S. Miller --- net/tipc/link.c | 3 +++ net/tipc/node.c | 5 +++-- 2 files changed, 6 insertions(+), 2 deletions(-) (limited to 'net') diff --git a/net/tipc/link.c b/net/tipc/link.c index 4ed650ce6e61..fb886b525d95 100644 --- a/net/tipc/link.c +++ b/net/tipc/link.c @@ -1516,6 +1516,9 @@ bool tipc_link_validate_msg(struct tipc_link *l, struct tipc_msg *hdr) return false; if (session != curr_session) return false; + /* Extra sanity check */ + if (!link_is_up(l) && msg_ack(hdr)) + return false; if (!(l->peer_caps & TIPC_LINK_PROTO_SEQNO)) return true; /* Accept only STATE with new sequence number */ diff --git a/net/tipc/node.c b/net/tipc/node.c index b0ee25f1f2e6..2afc4f8c37a7 100644 --- a/net/tipc/node.c +++ b/net/tipc/node.c @@ -913,6 +913,7 @@ void tipc_node_check_dest(struct net *net, u32 addr, bool reset = true; char *if_name; unsigned long intv; + u16 session; *dupl_addr = false; *respond = false; @@ -999,9 +1000,10 @@ void tipc_node_check_dest(struct net *net, u32 addr, goto exit; if_name = strchr(b->name, ':') + 1; + get_random_bytes(&session, sizeof(u16)); if (!tipc_link_create(net, if_name, b->identity, b->tolerance, b->net_plane, b->mtu, b->priority, - b->window, mod(tipc_net(net)->random), + b->window, session, tipc_own_addr(net), addr, peer_id, n->capabilities, tipc_bc_sndlink(n->net), n->bc_entry.link, @@ -1625,7 +1627,6 @@ static bool tipc_node_check_state(struct tipc_node *n, struct sk_buff *skb, tipc_link_create_dummy_tnl_msg(l, xmitq); n->failover_sent = true; } - /* If pkts arrive out of order, use lowest calculated syncpt */ if (less(syncpt, n->sync_point)) n->sync_point = syncpt; -- cgit v1.2.3-59-g8ed1b