netfilter: nat: fix src map lookup

commit 97772bcd56efa21d9d8976db6f205574ea602f51 upstream.

When doing initial conversion to rhashtable I replaced the bucket
walk with a single rhashtable_lookup_fast().

When moving to rhlist I failed to properly walk the list of identical
tuples, but that is what is needed for this to work correctly.
The table contains the original tuples, so the reply tuples are all
distinct.

We currently decide that mapping is (not) in range only based on the
first entry, but in case its not we need to try the reply tuple of the
next entry until we either find an in-range mapping or we checked
all the entries.

This bug makes nat core attempt collision resolution while it might be
able to use the mapping as-is.

Fixes: 870190a9ec90 ("netfilter: nat: convert nat bysrc hash to rhashtable")
Reported-by: Jaco Kroon <jaco@uls.co.za>
Tested-by: Jaco Kroon <jaco@uls.co.za>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/netfilter/nf_nat_core.c b/net/netfilter/nf_nat_core.c
index 6c72922d20caee83f498cb02cdce0c46899a1c22..b93a46ef812d295fbd9b05c1b396465b0507c2a3 100644 (file)
--- a/net/netfilter/nf_nat_core.c
+++ b/net/netfilter/nf_nat_core.c
@@ -222,20 +222,21 @@ find_appropriate_src(struct net *net,
                .tuple = tuple,
                .zone = zone
        };
-       struct rhlist_head *hl;
+       struct rhlist_head *hl, *h;
 
        hl = rhltable_lookup(&nf_nat_bysource_table, &key,
                             nf_nat_bysource_params);
-       if (!hl)
-               return 0;
 
-       ct = container_of(hl, typeof(*ct), nat_bysource);
+       rhl_for_each_entry_rcu(ct, h, hl, nat_bysource) {
+               nf_ct_invert_tuplepr(result,
+                                    &ct->tuplehash[IP_CT_DIR_REPLY].tuple);
+               result->dst = tuple->dst;
 
-       nf_ct_invert_tuplepr(result,
-                            &ct->tuplehash[IP_CT_DIR_REPLY].tuple);
-       result->dst = tuple->dst;
+               if (in_range(l3proto, l4proto, result, range))
+                       return 1;
+       }
 
-       return in_range(l3proto, l4proto, result, range);
+       return 0;
 }
 
 /* For [FUTURE] fragmentation handling, we want the least-used