netfilter: nat: add dependencies on conntrack module

MASQUERADE, S/DNAT and REDIRECT already call functions that depend on the
conntrack module.

However, since the conntrack hooks are now registered in a lazy fashion
(i.e., only when needed) a symbol reference is not enough.

Thus, when something is added to a nat table, make sure that it will see
packets by calling nf_ct_netns_get() which will register the conntrack
hooks in the current netns.

An alternative would be to add these dependencies to the NAT table.

However, that has problems when using non-modular builds -- we might
register e.g. ipv6 conntrack before its initcall has run, leading to NULL
deref crashes since its per-netns storage has not yet been allocated.

Adding the dependency in the modules instead has the advantage that nat
table also does not register its hooks until rules are added.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 9 insertions, 2 deletions

diff --git a/net/netfilter/xt_NETMAP.c b/net/netfilter/xt_NETMAP.c
index 94d0b5411192..e45a01255e70 100644
--- a/net/netfilter/xt_NETMAP.c
+++ b/net/netfilter/xt_NETMAP.c
@@ -60,7 +60,12 @@ static int netmap_tg6_checkentry(const struct xt_tgchk_param *par)
 
 	if (!(range->flags & NF_NAT_RANGE_MAP_IPS))
 		return -EINVAL;
-	return 0;
+	return nf_ct_netns_get(par->net, par->family);
+}
+
+static void netmap_tg_destroy(const struct xt_tgdtor_param *par)
+{
+	nf_ct_netns_put(par->net, par->family);
 }
 
 static unsigned int
@@ -111,7 +116,7 @@ static int netmap_tg4_check(const struct xt_tgchk_param *par)
 		pr_debug("bad rangesize %u.\n", mr->rangesize);
 		return -EINVAL;
 	}
-	return 0;
+	return nf_ct_netns_get(par->net, par->family);
 }
 
 static struct xt_target netmap_tg_reg[] __read_mostly = {
@@ -127,6 +132,7 @@ static struct xt_target netmap_tg_reg[] __read_mostly = {
 		              (1 << NF_INET_LOCAL_OUT) |
 		              (1 << NF_INET_LOCAL_IN),
 		.checkentry = netmap_tg6_checkentry,
+		.destroy    = netmap_tg_destroy,
 		.me         = THIS_MODULE,
 	},
 	{
@@ -141,6 +147,7 @@ static struct xt_target netmap_tg_reg[] __read_mostly = {
 		              (1 << NF_INET_LOCAL_OUT) |
 		              (1 << NF_INET_LOCAL_IN),
 		.checkentry = netmap_tg4_check,
+		.destroy    = netmap_tg_destroy,
 		.me         = THIS_MODULE,
 	},
 };