path: root/net
diff options
authorXin Long <lucien.xin@gmail.com>2016-09-10 23:11:23 +0800
committerDavid S. Miller <davem@davemloft.net>2016-09-13 11:44:58 -0400
commit715f5552b1e90ba3eecf6d1a6d044d0d5226663f (patch)
tree664441229dc29ce34920579093b0fcac85282626 /net
parent3e1be7ad2d38c6bd6aeef96df9bd0a7822f4e51c (diff)
sctp: hold the transport before using it in sctp_hash_cmp
Since commit 4f0087812648 ("sctp: apply rhashtable api to send/recv path"), sctp uses transport rhashtable with .obj_cmpfn sctp_hash_cmp, in which it compares the members of the transport with the rhashtable args to check if it's the right transport. But sctp uses the transport without holding it in sctp_hash_cmp, it can cause a use-after-free panic. As after it gets transport from hashtable, another CPU may close the sk and free the asoc. In sctp_association_free, it frees all the transports, meanwhile, the assoc's refcnt may be reduced to 0, assoc can be destroyed by sctp_association_destroy. So after that, transport->assoc is actually an unavailable memory address in sctp_hash_cmp. Although sctp_hash_cmp is under rcu_read_lock, it still can not avoid this, as assoc is not freed by RCU. This patch is to hold the transport before checking it's members with sctp_transport_hold, in which it checks the refcnt first, holds it if it's not 0. Fixes: 4f0087812648 ("sctp: apply rhashtable api to send/recv path") Signed-off-by: Xin Long <lucien.xin@gmail.com> Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
1 files changed, 17 insertions, 10 deletions
diff --git a/net/sctp/input.c b/net/sctp/input.c
index 69444d32ecda..1555fb8c68e0 100644
--- a/net/sctp/input.c
+++ b/net/sctp/input.c
@@ -796,27 +796,34 @@ struct sctp_hash_cmp_arg {
static inline int sctp_hash_cmp(struct rhashtable_compare_arg *arg,
const void *ptr)
+ struct sctp_transport *t = (struct sctp_transport *)ptr;
const struct sctp_hash_cmp_arg *x = arg->key;
- const struct sctp_transport *t = ptr;
- struct sctp_association *asoc = t->asoc;
- const struct net *net = x->net;
+ struct sctp_association *asoc;
+ int err = 1;
if (!sctp_cmp_addr_exact(&t->ipaddr, x->paddr))
- return 1;
- if (!net_eq(sock_net(asoc->base.sk), net))
- return 1;
+ return err;
+ if (!sctp_transport_hold(t))
+ return err;
+ asoc = t->asoc;
+ if (!net_eq(sock_net(asoc->base.sk), x->net))
+ goto out;
if (x->ep) {
if (x->ep != asoc->ep)
- return 1;
+ goto out;
} else {
if (x->laddr->v4.sin_port != htons(asoc->base.bind_addr.port))
- return 1;
+ goto out;
if (!sctp_bind_addr_match(&asoc->base.bind_addr,
x->laddr, sctp_sk(asoc->base.sk)))
- return 1;
+ goto out;
- return 0;
+ err = 0;
+ sctp_transport_put(t);
+ return err;
static inline u32 sctp_hash_obj(const void *data, u32 len, u32 seed)