kern/73321: Reproducible Panic (LOR: I4B / INET6)

[StefanEßer]

The following reply was made to PR kern/73321; it has been noted by GNATS.

From: Stefan =?iso-8859-1?Q?E=DFer?= <se at FreeBSD.org>
To: freebsd-gnats-submit at FreeBSD.org
Cc:  
Subject: Re: kern/73321: Reproducible Panic (LOR: I4B / INET6)
Date: Sat, 30 Oct 2004 23:36:59 +0200

 According to a message sent to the -current list by Jan Srzednicki
 in September, Robert Watson has added a check for a NULL pointer to
 the netperf branch:
 
 ==== //depot/user/rwatson/netperf/sys/netinet6/nd6.c#9 - /home/rwatson/p4/rwatson_netperf/sys/netinet6/nd6.c ====
 @@ -1779,6 +1779,8 @@                          
 	    nd6_slowtimo, NULL);
  	IFNET_RLOCK();         
  	for (ifp = TAILQ_FIRST(&ifnet); ifp; ifp = TAILQ_NEXT(ifp, if_list)) {
 +		if (ifp->if_afdata[AF_INET6] == NULL)
 + 			continue;
  		nd6if = ND_IFINFO(ifp);
  		if (nd6if->basereachable && /* already initialized */ 
 		    (nd6if->recalctm -= ND6_SLOWTIMER_INTERVAL) <= 0) {
 
 I have verified that this patch fixes the problem (or at least works
 around it) reliably. There could still be a race, if "NULL" is assigned
 to "ifp->if_afdata[AF_INET6]" immediately after the test and before the
 ND_IFINFO macro tries to use that pointer.
 
 I think this patch should be applied to -current and brought into 5.3
 since it fixes a real problem.