netfilter: ipset: Fix serious failure in CIDR tracking

This fixes a serious bug affecting all hash types with a net element -
specifically, if a CIDR value is deleted such that none of the same size
exist any more, all larger (less-specific) values will then fail to
match. Adding back any prefix with a CIDR equal to or more specific than
the one deleted will fix it.

Steps to reproduce:
ipset -N test hash:net
ipset -A test 1.1.0.0/16
ipset -A test 2.2.2.0/24
ipset -T test 1.1.1.1           #1.1.1.1 IS in set
ipset -D test 2.2.2.0/24
ipset -T test 1.1.1.1           #1.1.1.1 IS NOT in set

This is due to the fact that the nets counter was unconditionally
decremented prior to the iteration that shifts up the entries. Now, we
first check if there is a proceeding entry and if not, decrement it and
return. Otherwise, we proceed to iterate and then zero the last element,
which, in most cases, will already be zero.

Signed-off-by: Oliver Smith <oliver@8.c.9.b.0.7.4.0.1.0.0.2.ip6.arpa>
Signed-off-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>

diff --git a/net/netfilter/ipset/ip_set_hash_gen.h b/net/netfilter/ipset/ip_set_hash_gen.h
index 57beb1762b2de5f77031d79cd54f5903d246c3f7..707bc520d629f311dd9978d2e0bf222719f71c82 100644 (file)
--- a/net/netfilter/ipset/ip_set_hash_gen.h
+++ b/net/netfilter/ipset/ip_set_hash_gen.h
@@ -325,18 +325,22 @@ mtype_add_cidr(struct htype *h, u8 cidr, u8 nets_length)
 static void
 mtype_del_cidr(struct htype *h, u8 cidr, u8 nets_length)
 {
-       u8 i, j;
-
-       for (i = 0; i < nets_length - 1 && h->nets[i].cidr != cidr; i++)
-               ;
-       h->nets[i].nets--;
-
-       if (h->nets[i].nets != 0)
-               return;
-
-       for (j = i; j < nets_length - 1 && h->nets[j].nets; j++) {
-               h->nets[j].cidr = h->nets[j + 1].cidr;
-               h->nets[j].nets = h->nets[j + 1].nets;
+       u8 i, j, net_end = nets_length - 1;
+
+       for (i = 0; i < nets_length; i++) {
+               if (h->nets[i].cidr != cidr)
+                       continue;
+                if (h->nets[i].nets > 1 || i == net_end ||
+                    h->nets[i + 1].nets == 0) {
+                        h->nets[i].nets--;
+                        return;
+                }
+                for (j = i; j < net_end && h->nets[j].nets; j++) {
+                       h->nets[j].cidr = h->nets[j + 1].cidr;
+                       h->nets[j].nets = h->nets[j + 1].nets;
+                }
+                h->nets[j].nets = 0;
+                return;
        }
 }
 #endif