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 --- net/sctp/transport.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'net/sctp/transport.c') diff --git a/net/sctp/transport.c b/net/sctp/transport.c index aab9e3f29755..69f3799570a7 100644 --- a/net/sctp/transport.c +++ b/net/sctp/transport.c @@ -296,9 +296,9 @@ void sctp_transport_route(struct sctp_transport *transport, } /* Hold a reference to a transport. */ -void sctp_transport_hold(struct sctp_transport *transport) +int sctp_transport_hold(struct sctp_transport *transport) { - atomic_inc(&transport->refcnt); + return atomic_add_unless(&transport->refcnt, 1, 0); } /* Release a reference to a transport and clean up -- cgit