xfrm: Generate blackhole routes only from route lookup functions

klassert · klassert · commit f92ee61982d6 · 2014-09-16T10:08:40.000+02:00
Currently we genarate a blackhole route route whenever we have matching policies but can not resolve the states. Here we assume that dst_output() is called to kill the balckholed packets. Unfortunately this assumption is not true in all cases, so it is possible that these packets leave the system unwanted. We fix this by generating blackhole routes only from the route lookup functions, here we can guarantee a call to dst_output() afterwards. Fixes: 2774c13 ("xfrm: Handle blackhole route creation via afinfo.") Reported-by: Konstantinos Kolelis <k.kolelis@sirrix.com> Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
diff --git a/include/net/dst.h b/include/net/dst.h
@@ -490,7 +490,16 @@ static inline struct dst_entry *xfrm_lookup(struct net *net,
 					    int flags)
 {
 	return dst_orig;
-} 
+}
+
+static inline struct dst_entry *xfrm_lookup_route(struct net *net,
+						  struct dst_entry *dst_orig,
+						  const struct flowi *fl,
+						  struct sock *sk,
+						  int flags)
+{
+	return dst_orig;
+}
 
 static inline struct xfrm_state *dst_xfrm(const struct dst_entry *dst)
 {
@@ -502,6 +511,10 @@ struct dst_entry *xfrm_lookup(struct net *net, struct dst_entry *dst_orig,
 			      const struct flowi *fl, struct sock *sk,
 			      int flags);
 
+struct dst_entry *xfrm_lookup_route(struct net *net, struct dst_entry *dst_orig,
+				    const struct flowi *fl, struct sock *sk,
+				    int flags);
+
 /* skb attached with this dst needs transformation if dst->xfrm is valid */
 static inline struct xfrm_state *dst_xfrm(const struct dst_entry *dst)
 {
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
@@ -2265,9 +2265,9 @@ struct rtable *ip_route_output_flow(struct net *net, struct flowi4 *flp4,
 		return rt;
 
 	if (flp4->flowi4_proto)
-		rt = (struct rtable *) xfrm_lookup(net, &rt->dst,
-						   flowi4_to_flowi(flp4),
-						   sk, 0);
+		rt = (struct rtable *)xfrm_lookup_route(net, &rt->dst,
+							flowi4_to_flowi(flp4),
+							sk, 0);
 
 	return rt;
 }
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
@@ -1009,7 +1009,7 @@ struct dst_entry *ip6_dst_lookup_flow(struct sock *sk, struct flowi6 *fl6,
 	if (final_dst)
 		fl6->daddr = *final_dst;
 
-	return xfrm_lookup(sock_net(sk), dst, flowi6_to_flowi(fl6), sk, 0);
+	return xfrm_lookup_route(sock_net(sk), dst, flowi6_to_flowi(fl6), sk, 0);
 }
 EXPORT_SYMBOL_GPL(ip6_dst_lookup_flow);
 
@@ -1041,7 +1041,7 @@ struct dst_entry *ip6_sk_dst_lookup_flow(struct sock *sk, struct flowi6 *fl6,
 	if (final_dst)
 		fl6->daddr = *final_dst;
 
-	return xfrm_lookup(sock_net(sk), dst, flowi6_to_flowi(fl6), sk, 0);
+	return xfrm_lookup_route(sock_net(sk), dst, flowi6_to_flowi(fl6), sk, 0);
 }
 EXPORT_SYMBOL_GPL(ip6_sk_dst_lookup_flow);
 
diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
@@ -2138,7 +2138,7 @@ struct dst_entry *xfrm_lookup(struct net *net, struct dst_entry *dst_orig,
 			xfrm_pols_put(pols, drop_pols);
 			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTNOSTATES);
 
-			return make_blackhole(net, family, dst_orig);
+			return ERR_PTR(-EREMOTE);
 		}
 
 		err = -EAGAIN;
@@ -2195,6 +2195,22 @@ struct dst_entry *xfrm_lookup(struct net *net, struct dst_entry *dst_orig,
 }
 EXPORT_SYMBOL(xfrm_lookup);
 
+/* Callers of xfrm_lookup_route() must ensure a call to dst_output().
+ * Otherwise we may send out blackholed packets.
+ */
+struct dst_entry *xfrm_lookup_route(struct net *net, struct dst_entry *dst_orig,
+				    const struct flowi *fl,
+				    struct sock *sk, int flags)
+{
+	struct dst_entry *dst = xfrm_lookup(net, dst_orig, fl, sk, flags);
+
+	if (IS_ERR(dst) && PTR_ERR(dst) == -EREMOTE)
+		return make_blackhole(net, dst_orig->ops->family, dst_orig);
+
+	return dst;
+}
+EXPORT_SYMBOL(xfrm_lookup_route);
+
 static inline int
 xfrm_secpath_reject(int idx, struct sk_buff *skb, const struct flowi *fl)
 {

Original file line number	Diff line number	Diff line change
`@@ -1009,7 +1009,7 @@ struct dst_entry ip6_dst_lookup_flow(struct sock sk, struct flowi6 *fl6,`
`1009`	`1009`	`if (final_dst)`
`1010`	`1010`	`fl6->daddr = *final_dst;`
`1011`	`1011`
`1012`		`- return xfrm_lookup(sock_net(sk), dst, flowi6_to_flowi(fl6), sk, 0);`
	`1012`	`+ return xfrm_lookup_route(sock_net(sk), dst, flowi6_to_flowi(fl6), sk, 0);`
`1013`	`1013`	`}`
`1014`	`1014`	`EXPORT_SYMBOL_GPL(ip6_dst_lookup_flow);`
`1015`	`1015`
`@@ -1041,7 +1041,7 @@ struct dst_entry ip6_sk_dst_lookup_flow(struct sock sk, struct flowi6 *fl6,`
`1041`	`1041`	`if (final_dst)`
`1042`	`1042`	`fl6->daddr = *final_dst;`
`1043`	`1043`
`1044`		`- return xfrm_lookup(sock_net(sk), dst, flowi6_to_flowi(fl6), sk, 0);`
	`1044`	`+ return xfrm_lookup_route(sock_net(sk), dst, flowi6_to_flowi(fl6), sk, 0);`
`1045`	`1045`	`}`
`1046`	`1046`	`EXPORT_SYMBOL_GPL(ip6_sk_dst_lookup_flow);`
`1047`	`1047`