ipv6: Do not leak throw route references

While commit 73ba57bfae4a ("ipv6: fix backtracking for throw routes")
does good job on error propagation to the fib_rules_lookup()
in fib rules core framework that also corrects throw routes
handling, it does not solve route reference leakage problem
happened when we return -EAGAIN to the fib_rules_lookup()
and leave routing table entry referenced in arg->result.

If rule with matched throw route isn't last matched in the
list we overwrite arg->result losing reference on throw
route stored previously forever.

We also partially revert commit ab997ad40839 ("ipv6: fix the
incorrect return value of throw route") since we never return
routing table entry with dst.error == -EAGAIN when
CONFIG_IPV6_MULTIPLE_TABLES is on. Also there is no point
to check for RTF_REJECT flag since it is always set throw
route.

Fixes: 73ba57bfae4a ("ipv6: fix backtracking for throw routes")
Signed-off-by: Serhey Popovych <serhe.popovych@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 16 deletions

diff --git a/net/ipv6/fib6_rules.c b/net/ipv6/fib6_rules.c
index eea23b57c6a5..ec849d88a662 100644
--- a/net/ipv6/fib6_rules.c
+++ b/net/ipv6/fib6_rules.c
@@ -32,7 +32,6 @@ struct fib6_rule {
 struct dst_entry *fib6_rule_lookup(struct net *net, struct flowi6 *fl6,
                                    int flags, pol_lookup_t lookup)
 {
-        struct rt6_info *rt;
         struct fib_lookup_arg arg = {
                 .lookup_ptr = lookup,
                 .flags = FIB_LOOKUP_NOREF,
@@ -44,21 +43,11 @@ struct dst_entry *fib6_rule_lookup(struct net *net, struct flowi6 *fl6,
         fib_rules_lookup(net->ipv6.fib6_rules_ops,
                          flowi6_to_flowi(fl6), flags, &arg);
 
-        rt = arg.result;
+        if (arg.result)
+                return arg.result;
 
-        if (!rt) {
-                dst_hold(&net->ipv6.ip6_null_entry->dst);
-                return &net->ipv6.ip6_null_entry->dst;
-        }
-
-        if (rt->rt6i_flags & RTF_REJECT &&
-            rt->dst.error == -EAGAIN) {
-                ip6_rt_put(rt);
-                rt = net->ipv6.ip6_null_entry;
-                dst_hold(&rt->dst);
-        }
-
-        return &rt->dst;
+        dst_hold(&net->ipv6.ip6_null_entry->dst);
+        return &net->ipv6.ip6_null_entry->dst;
 }
 
 static int fib6_rule_action(struct fib_rule *rule, struct flowi *flp,
@@ -121,7 +110,8 @@ static int fib6_rule_action(struct fib_rule *rule, struct flowi *flp,
                         flp6->saddr = saddr;
                 }
                 err = rt->dst.error;
-                goto out;
+                if (err != -EAGAIN)
+                        goto out;
         }
 again:
         ip6_rt_put(rt);