sctp: fix panic when T2-shutdown timer expire on removed transport

If T2-shutdown timer is expired on a removed transport, kernel
panic will occur when we do failure management on that transport.
You can reproduce this use the following sequence:

  Endpoint A                           Endpoint B
  (ESTABLISHED)                        (ESTABLISHED)

                <-----------------      SHUTDOWN
                                        (SRC=X)
  ASCONF        ----------------->
  (Delete IP Address = X)
                <-----------------      ASCONF-ACK
                                        (Success Indication)
                <-----------------      SHUTDOWN
                                        (T2-shutdown timer expire)
This patch fixed the problem.

Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/net/sctp/associola.c b/net/sctp/associola.c
index e7b69a7360e2..3be28fed5915 100644
--- a/net/sctp/associola.c
+++ b/net/sctp/associola.c
@@ -567,6 +567,14 @@ void sctp_assoc_rm_peer(struct sctp_association *asoc,
         if (asoc->init_last_sent_to == peer)
                 asoc->init_last_sent_to = NULL;
 
+        /* If we remove the transport an SHUTDOWN was last sent to, set it
+         * to NULL. Combined with the update of the retran path above, this
+         * will cause the next SHUTDOWN to be sent to the next available
+         * transport, maintaining the cycle.
+         */
+        if (asoc->shutdown_last_sent_to == peer)
+                asoc->shutdown_last_sent_to = NULL;
+
         asoc->peer.transport_count--;
 
         sctp_transport_free(peer);