The code to handle the SIOCGLIFADDR and SIOCDLIFADDR ioctls in 
in6_lifaddr_ioctl() does not grab a reference to an ifnet address structure 
that it uses after dropping the IF_ADDR_LOCK().  Based on other code that uses 
a similar pattern of finding an ifa while under the lock and then using it 
after dropping the lock, I believe it should be acquiring a reference on the 
ifa and then dropping that reference when it is done using the ifa.  This 
(untested) patch should fix this I believe:

Index: in6.c
===================================================================
--- in6.c       (revision 228777)
+++ in6.c       (working copy)
@@ -1767,6 +1767,8 @@ in6_lifaddr_ioctl(struct socket *so, u_long cmd, c
                        if (IN6_ARE_ADDR_EQUAL(&candidate, &match))
                                break;
                }
+               if (ifa != NULL)
+                       ifa_ref(ifa);
                IF_ADDR_UNLOCK(ifp);
                if (!ifa)
                        return EADDRNOTAVAIL;
@@ -1779,16 +1781,20 @@ in6_lifaddr_ioctl(struct socket *so, u_long cmd, c
                        bcopy(&ia->ia_addr, &iflr->addr, ia->ia_addr.sin6_len);
                        error = sa6_recoverscope(
                            (struct sockaddr_in6 *)&iflr->addr);
-                       if (error != 0)
+                       if (error != 0) {
+                               ifa_free(ifa);
                                return (error);
+                       }
 
                        if ((ifp->if_flags & IFF_POINTOPOINT) != 0) {
                                bcopy(&ia->ia_dstaddr, &iflr->dstaddr,
                                    ia->ia_dstaddr.sin6_len);
                                error = sa6_recoverscope(
                                    (struct sockaddr_in6 *)&iflr->dstaddr);
-                               if (error != 0)
+                               if (error != 0) {
+                                       ifa_free(ifa);
                                        return (error);
+                               }
                        } else
                                bzero(&iflr->dstaddr, sizeof(iflr->dstaddr));
 
@@ -1796,6 +1802,7 @@ in6_lifaddr_ioctl(struct socket *so, u_long cmd, c
                            in6_mask2len(&ia->ia_prefixmask.sin6_addr, NULL);
 
                        iflr->flags = ia->ia6_flags;    /* XXX */
+                       ifa_free(ifa);
 
                        return 0;
                } else {
@@ -1819,6 +1826,7 @@ in6_lifaddr_ioctl(struct socket *so, u_long cmd, c
                            ia->ia_prefixmask.sin6_len);
 
                        ifra.ifra_flags = ia->ia6_flags;
+                       ifa_free(ifa);
                        return in6_control(so, SIOCDIFADDR_IN6, (caddr_t)&ifra,
                            ifp, td);
                }


-- 
John Baldwin
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