[SCTP]: Fix potential race condition between sctp_close() and sctp_rcv().

Do not release the reference to association/endpoint if an incoming skb is
added to backlog. Instead release it after the chunk is processed in
sctp_backlog_rcv().

Signed-off-by: Sridhar Samudrala <sri@us.ibm.com>
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>

1 files changed, 20 insertions, 9 deletions

diff --git a/net/sctp/input.c b/net/sctp/input.c
index 4aa6fc60357c..c463e4049c52 100644
--- a/net/sctp/input.c
+++ b/net/sctp/input.c
@@ -262,15 +262,12 @@ int sctp_rcv(struct sk_buff *skb)
         else
                 sctp_backlog_rcv(sk, skb);
 
-        /* Release the sock and any reference counts we took in the
-         * lookup calls.
+        /* Release the sock and the sock ref we took in the lookup calls. 
+         * The asoc/ep ref will be released in sctp_backlog_rcv.
          */
         sctp_bh_unlock_sock(sk);
-        if (asoc)
-                sctp_association_put(asoc);
-        else
-                sctp_endpoint_put(ep);
         sock_put(sk);
+
         return ret;
 
 discard_it:
@@ -296,9 +293,23 @@ discard_release:
 int sctp_backlog_rcv(struct sock *sk, struct sk_buff *skb)
 {
         struct sctp_chunk *chunk = SCTP_INPUT_CB(skb)->chunk;
-        struct sctp_inq *inqueue = &chunk->rcvr->inqueue;
-
-        sctp_inq_push(inqueue, chunk);
+        struct sctp_inq *inqueue = NULL;
+        struct sctp_ep_common *rcvr = NULL;
+
+        rcvr = chunk->rcvr;
+        if (rcvr->dead) {
+                sctp_chunk_free(chunk);
+        } else {
+                inqueue = &chunk->rcvr->inqueue;
+                sctp_inq_push(inqueue, chunk);
+        }
+
+        /* Release the asoc/ep ref we took in the lookup calls in sctp_rcv. */ 
+        if (SCTP_EP_TYPE_ASSOCIATION == rcvr->type)
+                sctp_association_put(sctp_assoc(rcvr));
+        else
+                sctp_endpoint_put(sctp_ep(rcvr));
+  
         return 0;
 }