[SCTP]: Set assoc_id correctly during INIT collision.

During the INIT/COOKIE-ACK collision cases, it's possible to get
into a situation where the association id is not yet set at the time
of the user event generation.  As a result, user events have an
association id set to 0 which will confuse applications.

This happens if we hit case B of duplicate cookie processing.
In the particular example found and provided by Oscar Isaula
<Oscar.Isaula@motorola.com>, flow looks like this:
A				B
---- INIT------->  (lost)
	    <---------INIT------
---- INIT-ACK--->
	    <------ Cookie ECHO

When the Cookie Echo is received, we end up trying to update the
association that was created on A as a result of the (lost) INIT,
but that association doesn't have the ID set yet.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 29 insertions, 0 deletions

diff --git a/net/sctp/associola.c b/net/sctp/associola.c
index db73ef9..df94e3c 100644
--- a/net/sctp/associola.c
+++ b/net/sctp/associola.c
@@ -1103,6 +1103,13 @@ void sctp_assoc_update(struct sctp_association *asoc,
 			asoc->ssnmap = new->ssnmap;
 			new->ssnmap = NULL;
 		}
+
+		if (!asoc->assoc_id) {
+			/* get a new association id since we don't have one
+			 * yet.
+			 */
+			sctp_assoc_set_id(asoc, GFP_ATOMIC);
+		}
 	}
 }
 
@@ -1375,3 +1382,25 @@ out:
 	sctp_read_unlock(&asoc->base.addr_lock);
 	return found;
 }
+
+/* Set an association id for a given association */
+int sctp_assoc_set_id(struct sctp_association *asoc, gfp_t gfp)
+{
+	int assoc_id;
+	int error = 0;
+retry:
+	if (unlikely(!idr_pre_get(&sctp_assocs_id, gfp)))
+		return -ENOMEM;
+
+	spin_lock_bh(&sctp_assocs_id_lock);
+	error = idr_get_new_above(&sctp_assocs_id, (void *)asoc,
+				    1, &assoc_id);
+	spin_unlock_bh(&sctp_assocs_id_lock);
+	if (error == -EAGAIN)
+		goto retry;
+	else if (error)
+		return error;
+
+	asoc->assoc_id = (sctp_assoc_t) assoc_id;
+	return error;
+}