Fix a route table leak in rtalloc() and rtalloc_ign(). It is

possible for ro->ro_rt to be non-NULL even though the RTF_UP flag
is cleared.  (Example: a routing daemon or the "route" command
deletes a cloned route in active use by a TCP connection.)  In that
case, the code was clobbering a reference to the routing table
entry without decrementing the entry's reference count.

The splnet() call probably isn't needed, but I haven't been able
to prove that yet.  It isn't significant from a performance standpoint
since it is executed very rarely.

Reviewed by:	wollman and others in the freebsd-current mailing list

1 files changed, 12 insertions, 5 deletions

diff --git a/sys/net/route.c b/sys/net/route.c
index 04608f5..45e0e39 100644
--- a/sys/net/route.c
+++ b/sys/net/route.c
@@ -88,9 +88,7 @@ void
 rtalloc(ro)
 	register struct route *ro;
 {
-	if (ro->ro_rt && ro->ro_rt->rt_ifp && (ro->ro_rt->rt_flags & RTF_UP))
-		return;				 /* XXX */
-	ro->ro_rt = rtalloc1(&ro->ro_dst, 1, 0UL);
+	rtalloc_ign(ro, 0UL);
 }
 
 void
@@ -98,8 +96,17 @@ rtalloc_ign(ro, ignore)
 	register struct route *ro;
 	u_long ignore;
 {
-	if (ro->ro_rt && ro->ro_rt->rt_ifp && (ro->ro_rt->rt_flags & RTF_UP))
-		return;				 /* XXX */
+	struct rtentry *rt;
+	int s;
+
+	if ((rt = ro->ro_rt) != NULL) {
+		if (rt->rt_ifp != NULL && rt->rt_flags & RTF_UP)
+			return;
+		/* XXX - We are probably always at splnet here already. */
+		s = splnet();
+		RTFREE(rt);
+		splx(s);
+	}
 	ro->ro_rt = rtalloc1(&ro->ro_dst, 1, ignore);
 }