svn commit: r341087 - stable/11/sys/netinet6

[Eric van Gyzen]

Author: vangyzen
Date: Tue Nov 27 19:40:18 2018
New Revision: 341087
URL: https://svnweb.freebsd.org/changeset/base/341087

Log:
  MFC r340257
  
  in6_ifattach_linklocal: handle immediate removal of the new LLA
  
  If another thread immediately removes the link-local address
  added by in6_update_ifa(), in6ifa_ifpforlinklocal() can return NULL,
  so the following assertion (or dereference) is wrong.
  Remove the assertion, and handle NULL somewhat better than panicking.
  This matches all of the other callers of in6_update_ifa().
  
  PR:		219250
  Reviewed by:	bz, dab (both an earlier version)
  Sponsored by:	Dell EMC Isilon
  Differential Revision:	https://reviews.freebsd.org/D17898

Modified:
  stable/11/sys/netinet6/in6_ifattach.c
Directory Properties:
  stable/11/   (props changed)

Modified: stable/11/sys/netinet6/in6_ifattach.c
==============================================================================
--- stable/11/sys/netinet6/in6_ifattach.c	Tue Nov 27 19:40:07 2018	(r341086)
+++ stable/11/sys/netinet6/in6_ifattach.c	Tue Nov 27 19:40:18 2018	(r341087)
@@ -502,9 +502,16 @@ in6_ifattach_linklocal(struct ifnet *ifp, struct ifnet
 		return (-1);
 	}
 
-	ia = in6ifa_ifpforlinklocal(ifp, 0); /* ia must not be NULL */
-	KASSERT(ia != NULL, ("%s: ia == NULL, ifp=%p", __func__, ifp));
-
+	ia = in6ifa_ifpforlinklocal(ifp, 0);
+	if (ia == NULL) {
+		/*
+		 * Another thread removed the address that we just added.
+		 * This should be rare, but it happens.
+		 */
+		nd6log((LOG_NOTICE, "%s: %s: new link-local address "
+			"disappeared\n", __func__, if_name(ifp)));
+		return (-1);
+	}
 	ifa_free(&ia->ia_ifa);
 
 	/*