tipc: Fix node lock reclamation issues in broadcast link reception

Fixes a pair of problems in broadcast link message reception code
relating to the reclamation of the node lock after consuming an
in-sequence message.

1) Now retests to see if the sending node is still up after reclaiming
   the node lock, and bails out if it is non-operational.

2) Now manipulates the node's deferred message queue only after
   reclaiming the node lock, rather than using queue head pointer
   information that was cached previously.

Signed-off-by: Allan Stephens <allan.stephens@windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

1 files changed, 40 insertions, 18 deletions

diff --git a/net/tipc/bcast.c b/net/tipc/bcast.c
index 7342abc2cfa1..e7df313020ce 100644
--- a/net/tipc/bcast.c
+++ b/net/tipc/bcast.c
@@ -474,7 +474,7 @@ void tipc_bclink_recv_pkt(struct sk_buff *buf)
         struct tipc_node *node;
         u32 next_in;
         u32 seqno;
-        struct sk_buff *deferred;
+        int deferred;
 
         /* Screen out unwanted broadcast messages */
 
@@ -489,6 +489,8 @@ void tipc_bclink_recv_pkt(struct sk_buff *buf)
         if (unlikely(!node->bclink.supported))
                 goto unlock;
 
+        /* Handle broadcast protocol message */
+
         if (unlikely(msg_user(msg) == BCAST_PROTOCOL)) {
                 if (msg_type(msg) != STATE_MSG)
                         goto unlock;
@@ -513,11 +515,11 @@ void tipc_bclink_recv_pkt(struct sk_buff *buf)
 
         /* Handle in-sequence broadcast message */
 
-receive:
-        next_in = mod(node->bclink.last_in + 1);
         seqno = msg_seqno(msg);
+        next_in = mod(node->bclink.last_in + 1);
 
         if (likely(seqno == next_in)) {
+receive:
                 bcl->stats.recv_info++;
                 node->bclink.last_in++;
                 bclink_set_gap(node);
@@ -551,23 +553,40 @@ receive:
                         buf_discard(buf);
                 }
                 buf = NULL;
+
+                /* Determine new synchronization state */
+
                 tipc_node_lock(node);
-                deferred = node->bclink.deferred_head;
-                if (deferred && (buf_seqno(deferred) == mod(next_in + 1))) {
-                        buf = deferred;
-                        msg = buf_msg(buf);
-                        node->bclink.deferred_head = deferred->next;
-                        goto receive;
-                }
-        } else if (less(next_in, seqno)) {
+                if (unlikely(!tipc_node_is_up(node)))
+                        goto unlock;
+
+                if (!node->bclink.deferred_head)
+                        goto unlock;
+
+                msg = buf_msg(node->bclink.deferred_head);
+                seqno = msg_seqno(msg);
+                next_in = mod(next_in + 1);
+                if (seqno != next_in)
+                        goto unlock;
+
+                /* Take in-sequence message from deferred queue & deliver it */
+
+                buf = node->bclink.deferred_head;
+                node->bclink.deferred_head = buf->next;
+                goto receive;
+        }
+
+        /* Handle out-of-sequence broadcast message */
+
+        if (less(next_in, seqno)) {
                 u32 gap_after = node->bclink.gap_after;
                 u32 gap_to = node->bclink.gap_to;
 
-                if (tipc_link_defer_pkt(&node->bclink.deferred_head,
-                                        &node->bclink.deferred_tail,
-                                        buf)) {
+                deferred = tipc_link_defer_pkt(&node->bclink.deferred_head,
+                                               &node->bclink.deferred_tail,
+                                               buf);
+                if (deferred) {
                         node->bclink.nack_sync++;
-                        bcl->stats.deferred_recv++;
                         if (seqno == mod(gap_after + 1))
                                 node->bclink.gap_after = seqno;
                         else if (less(gap_after, seqno) && less(seqno, gap_to))
@@ -579,9 +598,12 @@ receive:
                                 bclink_send_nack(node);
                         bclink_set_gap(node);
                 }
-        } else {
-                bcl->stats.duplicates++;
-        }
+        } else
+                deferred = 0;
+
+        if (deferred)
+                bcl->stats.deferred_recv++;
+
 unlock:
         tipc_node_unlock(node);
 exit: