From 1eed677933b816978abc4e3e18ecae5f254cb9be Mon Sep 17 00:00:00 2001 From: Xin Long Date: Fri, 22 Jan 2016 01:49:07 +0800 Subject: sctp: fix the transport dead race check by using atomic_add_unless on refcnt Now when __sctp_lookup_association is running in BH, it will try to check if t->dead is set, but meanwhile other CPUs may be freeing this transport and this assoc and if it happens that __sctp_lookup_association checked t->dead a bit too early, it may think that the association is still good while it was already freed. So we fix this race by using atomic_add_unless in sctp_transport_hold. After we get one transport from hashtable, we will hold it only when this transport's refcnt is not 0, so that we can make sure t->asoc cannot be freed before we hold the asoc again. Note that sctp association is not freed using RCU so we can't use atomic_add_unless() with it as it may just be too late for that either. Fixes: 4f0087812648 ("sctp: apply rhashtable api to send/recv path") Reported-by: Vlad Yasevich Signed-off-by: Xin Long Signed-off-by: Marcelo Ricardo Leitner Signed-off-by: David S. Miller --- include/net/sctp/structs.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/net/sctp/structs.h') diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h index 20e72129be1c..344da04e2e30 100644 --- a/include/net/sctp/structs.h +++ b/include/net/sctp/structs.h @@ -955,7 +955,7 @@ void sctp_transport_route(struct sctp_transport *, union sctp_addr *, void sctp_transport_pmtu(struct sctp_transport *, struct sock *sk); void sctp_transport_free(struct sctp_transport *); void sctp_transport_reset_timers(struct sctp_transport *); -void sctp_transport_hold(struct sctp_transport *); +int sctp_transport_hold(struct sctp_transport *); void sctp_transport_put(struct sctp_transport *); void sctp_transport_update_rto(struct sctp_transport *, __u32); void sctp_transport_raise_cwnd(struct sctp_transport *, __u32, __u32); -- cgit v1.2.3 From 47faa1e4c50ec26e6e75dcd1ce53f064bd45f729 Mon Sep 17 00:00:00 2001 From: Xin Long Date: Fri, 22 Jan 2016 01:49:09 +0800 Subject: sctp: remove the dead field of sctp_transport After we use refcnt to check if transport is alive, the dead can be removed from sctp_transport. The traversal of transport_addr_list in procfs dump is using list_for_each_entry_rcu, no need to check if it has been freed. sctp_generate_t3_rtx_event and sctp_generate_heartbeat_event is protected by sock lock, it's not necessary to check dead, either. also, the timers are cancelled when sctp_transport_free() is called, that it doesn't wait for refcnt to reach 0 to cancel them. Signed-off-by: Xin Long Signed-off-by: Marcelo Ricardo Leitner Signed-off-by: David S. Miller --- include/net/sctp/structs.h | 3 +-- net/sctp/proc.c | 4 ---- net/sctp/sm_sideeffect.c | 12 ------------ net/sctp/transport.c | 4 +--- 4 files changed, 2 insertions(+), 21 deletions(-) (limited to 'include/net/sctp/structs.h') diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h index 344da04e2e30..205630bb5010 100644 --- a/include/net/sctp/structs.h +++ b/include/net/sctp/structs.h @@ -756,7 +756,6 @@ struct sctp_transport { /* Reference counting. */ atomic_t refcnt; - __u32 dead:1, /* RTO-Pending : A flag used to track if one of the DATA * chunks sent to this address is currently being * used to compute a RTT. If this flag is 0, @@ -766,7 +765,7 @@ struct sctp_transport { * calculation completes (i.e. the DATA chunk * is SACK'd) clear this flag. */ - rto_pending:1, + __u32 rto_pending:1, /* * hb_sent : a flag that signals that we have a pending diff --git a/net/sctp/proc.c b/net/sctp/proc.c index c74a810150aa..ded7d931a6a5 100644 --- a/net/sctp/proc.c +++ b/net/sctp/proc.c @@ -165,8 +165,6 @@ static void sctp_seq_dump_remote_addrs(struct seq_file *seq, struct sctp_associa list_for_each_entry_rcu(transport, &assoc->peer.transport_addr_list, transports) { addr = &transport->ipaddr; - if (transport->dead) - continue; af = sctp_get_af_specific(addr->sa.sa_family); if (af->cmp_addr(addr, primary)) { @@ -499,8 +497,6 @@ static int sctp_remaddr_seq_show(struct seq_file *seq, void *v) list_for_each_entry_rcu(tsp, &assoc->peer.transport_addr_list, transports) { - if (tsp->dead) - continue; /* * The remote address (ADDR) */ diff --git a/net/sctp/sm_sideeffect.c b/net/sctp/sm_sideeffect.c index 2e21384697c2..b5327bb77458 100644 --- a/net/sctp/sm_sideeffect.c +++ b/net/sctp/sm_sideeffect.c @@ -259,12 +259,6 @@ void sctp_generate_t3_rtx_event(unsigned long peer) goto out_unlock; } - /* Is this transport really dead and just waiting around for - * the timer to let go of the reference? - */ - if (transport->dead) - goto out_unlock; - /* Run through the state machine. */ error = sctp_do_sm(net, SCTP_EVENT_T_TIMEOUT, SCTP_ST_TIMEOUT(SCTP_EVENT_TIMEOUT_T3_RTX), @@ -380,12 +374,6 @@ void sctp_generate_heartbeat_event(unsigned long data) goto out_unlock; } - /* Is this structure just waiting around for us to actually - * get destroyed? - */ - if (transport->dead) - goto out_unlock; - error = sctp_do_sm(net, SCTP_EVENT_T_TIMEOUT, SCTP_ST_TIMEOUT(SCTP_EVENT_TIMEOUT_HEARTBEAT), asoc->state, asoc->ep, asoc, diff --git a/net/sctp/transport.c b/net/sctp/transport.c index 69f3799570a7..a431c14044a4 100644 --- a/net/sctp/transport.c +++ b/net/sctp/transport.c @@ -132,8 +132,6 @@ fail: */ void sctp_transport_free(struct sctp_transport *transport) { - transport->dead = 1; - /* Try to delete the heartbeat timer. */ if (del_timer(&transport->hb_timer)) sctp_transport_put(transport); @@ -169,7 +167,7 @@ static void sctp_transport_destroy_rcu(struct rcu_head *head) */ static void sctp_transport_destroy(struct sctp_transport *transport) { - if (unlikely(!transport->dead)) { + if (unlikely(atomic_read(&transport->refcnt))) { WARN(1, "Attempt to destroy undead transport %p!\n", transport); return; } -- cgit v1.2.3