diff options
| author | Xin Long <lucien.xin@gmail.com> | 2016-01-22 01:49:07 +0800 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2016-01-28 15:59:32 -0800 |
| commit | 1eed677933b816978abc4e3e18ecae5f254cb9be (patch) | |
| tree | b2eba8266b9f81c2a93d9cb9173962da88fd1399 /net | |
| parent | 2baaa2d1386bd9949877a74ffc0dc0f2c5394b85 (diff) | |
| download | linux-1eed677933b816978abc4e3e18ecae5f254cb9be.tar.bz2 | |
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 <vyasevich@gmail.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
| -rw-r--r-- | net/sctp/input.c | 17 | ||||
| -rw-r--r-- | net/sctp/transport.c | 4 |
2 files changed, 13 insertions, 8 deletions
diff --git a/net/sctp/input.c b/net/sctp/input.c index bf61dfb8e09e..49d2cc751386 100644 --- a/net/sctp/input.c +++ b/net/sctp/input.c @@ -935,15 +935,22 @@ static struct sctp_association *__sctp_lookup_association( struct sctp_transport **pt) { struct sctp_transport *t; + struct sctp_association *asoc = NULL; + rcu_read_lock(); t = sctp_addrs_lookup_transport(net, local, peer); - if (!t || t->dead) - return NULL; + if (!t || !sctp_transport_hold(t)) + goto out; - sctp_association_hold(t->asoc); + asoc = t->asoc; + sctp_association_hold(asoc); *pt = t; - return t->asoc; + sctp_transport_put(t); + +out: + rcu_read_unlock(); + return asoc; } /* Look up an association. protected by RCU read lock */ @@ -955,9 +962,7 @@ struct sctp_association *sctp_lookup_association(struct net *net, { struct sctp_association *asoc; - rcu_read_lock(); asoc = __sctp_lookup_association(net, laddr, paddr, transportp); - rcu_read_unlock(); return asoc; } 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 |