Author: asomers
Date: Fri May  2 16:24:09 2014
New Revision: 265232
URL: http://svnweb.freebsd.org/changeset/base/265232

Log:
  Fix a panic caused by doing "ifconfig -am" while a lagg is being destroyed.
  The thread that is destroying the lagg has already set sc->sc_psc=NULL when
  the "ifconfig -am" thread gets to lacp_req().  It tries to dereference
  sc->sc_psc and panics.  The solution is for lacp_req() to check the value of
  sc->sc_psc.  If NULL, harmlessly return an lacp_opreq structure full of
  zeros.  Full details in GNATS.
  
  PR:           kern/189003
  Reviewed by:  timeout on freebsd-net@
  MFC after:    3 weeks
  Sponsored by: Spectra Logic Corporation

Modified:
  head/sys/net/ieee8023ad_lacp.c

Modified: head/sys/net/ieee8023ad_lacp.c
==============================================================================
--- head/sys/net/ieee8023ad_lacp.c      Fri May  2 16:15:34 2014        
(r265231)
+++ head/sys/net/ieee8023ad_lacp.c      Fri May  2 16:24:09 2014        
(r265232)
@@ -590,10 +590,20 @@ lacp_req(struct lagg_softc *sc, caddr_t 
 {
        struct lacp_opreq *req = (struct lacp_opreq *)data;
        struct lacp_softc *lsc = LACP_SOFTC(sc);
-       struct lacp_aggregator *la = lsc->lsc_active_aggregator;
+       struct lacp_aggregator *la;
 
-       LACP_LOCK(lsc);
        bzero(req, sizeof(struct lacp_opreq));
+       
+       /* 
+        * If the LACP softc is NULL, return with the opreq structure full of
+        * zeros.  It is normal for the softc to be NULL while the lagg is
+        * being destroyed.
+        */
+       if (NULL == lsc)
+               return;
+
+       la = lsc->lsc_active_aggregator;
+       LACP_LOCK(lsc);
        if (la != NULL) {
                req->actor_prio = ntohs(la->la_actor.lip_systemid.lsi_prio);
                memcpy(&req->actor_mac, &la->la_actor.lip_systemid.lsi_mac,
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