kern/82919: Bridge configuration update will crash the system in 5.4

[LiangYi]

>Number:         82919
>Category:       kern
>Synopsis:       Bridge configuration update will crash the system in 5.4
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sun Jul 03 10:00:32 GMT 2005
>Closed-Date:
>Last-Modified:
>Originator:     LiangYi
>Release:        FreeBSD 5.4-RELEASE
>Organization:
lingzhou network Inc
>Environment:
FreeBSD bsd.lingzhou.com.cn 5.4-RELEASE FreeBSD 5.4-RELEASE #0
>Description:
Setup a bridge like this
	sysctl -w net.link.ether.bridge_cfg="em0:1,em1:1"
Generate some traffic on this bridge
Update the bridge configuration like this
	sysctl -w net.link.ether.bridge_cfg="em1:1,em2:1"
System will crash randomly.

>How-To-Repeat:

>Fix:
--- bridge.c.orig       Sun Jul  3 17:31:55 2005
+++ bridge.c    Sun Jul  3 17:33:17 2005
@@ -767,13 +767,19 @@
     struct ifnet *dst, *old;
     bdg_hash_table *bt;                        /* location in hash table */
     int dropit = BDG_MUTED(ifp);
+    struct cluster_softc *clp;
 
     /*
      * hash the source address
      */
     BDG_LOCK();
     index = HASH_FN(eh->ether_shost);
-    bt = &BDG_CLUSTER(ifp)->ht[index];
+    clp = BDG_CLUSTER(ifp);
+    if(clp==NULL) {
+       BDG_UNLOCK();
+       return BDG_DROP;
+    }
+    bt = &clp->ht[index];
     bt->used = 1;
     old = bt->name;
     if (old) {                         /* the entry is valid */

>Release-Note:
>Audit-Trail:
>Unformatted: