icmp: Fix regression in nexthop resolution during replies.

icmp_route_lookup() uses the wrong flow parameters if the reverse
session route lookup isn't used.

So do not commit to the re-decoded flow until we actually make a
final decision to use a real route saved in 'rt2'.

Reported-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 6 deletions

diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index 5395e45dcce6..23ef31baa1af 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -380,6 +380,7 @@ static struct rtable *icmp_route_lookup(struct net *net,
                                         struct icmp_bxm *param)
 {
         struct rtable *rt, *rt2;
+        struct flowi4 fl4_dec;
         int err;
 
         memset(fl4, 0, sizeof(*fl4));
@@ -408,19 +409,19 @@ static struct rtable *icmp_route_lookup(struct net *net,
         } else
                 return rt;
 
-        err = xfrm_decode_session_reverse(skb_in, flowi4_to_flowi(fl4), AF_INET);
+        err = xfrm_decode_session_reverse(skb_in, flowi4_to_flowi(&fl4_dec), AF_INET);
         if (err)
                 goto relookup_failed;
 
-        if (inet_addr_type(net, fl4->saddr) == RTN_LOCAL) {
-                rt2 = __ip_route_output_key(net, fl4);
+        if (inet_addr_type(net, fl4_dec.saddr) == RTN_LOCAL) {
+                rt2 = __ip_route_output_key(net, &fl4_dec);
                 if (IS_ERR(rt2))
                         err = PTR_ERR(rt2);
         } else {
                 struct flowi4 fl4_2 = {};
                 unsigned long orefdst;
 
-                fl4_2.daddr = fl4->saddr;
+                fl4_2.daddr = fl4_dec.saddr;
                 rt2 = ip_route_output_key(net, &fl4_2);
                 if (IS_ERR(rt2)) {
                         err = PTR_ERR(rt2);
@@ -428,7 +429,7 @@ static struct rtable *icmp_route_lookup(struct net *net,
                 }
                 /* Ugh! */
                 orefdst = skb_in->_skb_refdst; /* save old refdst */
-                err = ip_route_input(skb_in, fl4->daddr, fl4->saddr,
+                err = ip_route_input(skb_in, fl4_dec.daddr, fl4_dec.saddr,
                                      RT_TOS(tos), rt2->dst.dev);
 
                 dst_release(&rt2->dst);
@@ -440,10 +441,11 @@ static struct rtable *icmp_route_lookup(struct net *net,
                 goto relookup_failed;
 
         rt2 = (struct rtable *) xfrm_lookup(net, &rt2->dst,
-                                            flowi4_to_flowi(fl4), NULL,
+                                            flowi4_to_flowi(&fl4_dec), NULL,
                                             XFRM_LOOKUP_ICMP);
         if (!IS_ERR(rt2)) {
                 dst_release(&rt->dst);
+                memcpy(fl4, &fl4_dec, sizeof(*fl4));
                 rt = rt2;
         } else if (PTR_ERR(rt2) == -EPERM) {
                 if (rt)