From e1f203488cc652bbb6b062bf1eb454982e95cca6 Mon Sep 17 00:00:00 2001
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Fri, 25 Nov 2016 21:14:50 +0100
Subject: ratelimiter: load hashlimit at modinsert time

This fixes a potential race with net_lock and rtnl_lock.
---
 src/ratelimiter.c | 81 +++++++++++++++++++++++++++++++------------------------
 1 file changed, 46 insertions(+), 35 deletions(-)

(limited to 'src/ratelimiter.c')

diff --git a/src/ratelimiter.c b/src/ratelimiter.c
index 8bfe46b..7c23d55 100644
--- a/src/ratelimiter.c
+++ b/src/ratelimiter.c
@@ -15,6 +15,11 @@
 #error "WireGuard requires CONFIG_IP6_NF_IPTABLES when using CONFIG_IPV6."
 #endif
 
+static struct xt_match *v4_match;
+#if IS_ENABLED(CONFIG_IPV6)
+static struct xt_match *v6_match;
+#endif
+
 enum {
 	RATELIMITER_PACKETS_PER_SECOND = 75,
 	RATELIMITER_PACKETS_BURSTABLE = 5
@@ -44,47 +49,29 @@ int ratelimiter_init(struct ratelimiter *ratelimiter, struct wireguard_device *w
 	memset(ratelimiter, 0, sizeof(struct ratelimiter));
 
 	cfg_init(&ratelimiter->v4_info.cfg, NFPROTO_IPV4);
-	cfg_init(&ratelimiter->v6_info.cfg, NFPROTO_IPV6);
 	memcpy(ratelimiter->v4_info.name, dev->name, IFNAMSIZ);
-	memcpy(ratelimiter->v6_info.name, dev->name, IFNAMSIZ);
-
-	ratelimiter->v4_match = xt_request_find_match(NFPROTO_IPV4, "hashlimit", 1);
-	if (IS_ERR(ratelimiter->v4_match)) {
-		pr_err("The xt_hashlimit module for IPv4 is required");
-		return PTR_ERR(ratelimiter->v4_match);
-	}
-
 	chk.matchinfo = &ratelimiter->v4_info;
-	chk.match = ratelimiter->v4_match;
+	chk.match = v4_match;
 	chk.family = NFPROTO_IPV4;
-	ret = ratelimiter->v4_match->checkentry(&chk);
-	if (ret < 0) {
-		module_put(ratelimiter->v4_match->me);
+	ret = v4_match->checkentry(&chk);
+	if (ret < 0)
 		return ret;
-	}
 
 #if IS_ENABLED(CONFIG_IPV6)
-	ratelimiter->v6_match = xt_request_find_match(NFPROTO_IPV6, "hashlimit", 1);
-	if (IS_ERR(ratelimiter->v6_match)) {
-		pr_err("The xt_hashlimit module for IPv6 is required");
-		module_put(ratelimiter->v4_match->me);
-		return PTR_ERR(ratelimiter->v6_match);
-	}
-
+	cfg_init(&ratelimiter->v6_info.cfg, NFPROTO_IPV6);
+	memcpy(ratelimiter->v6_info.name, dev->name, IFNAMSIZ);
 	chk.matchinfo = &ratelimiter->v6_info;
-	chk.match = ratelimiter->v6_match;
+	chk.match = v6_match;
 	chk.family = NFPROTO_IPV6;
-	ret = ratelimiter->v6_match->checkentry(&chk);
+	ret = v6_match->checkentry(&chk);
 	if (ret < 0) {
 		struct xt_mtdtor_param dtor_v4 = {
 			.net = wg->creating_net,
-			.match = ratelimiter->v4_match,
+			.match = v4_match,
 			.matchinfo = &ratelimiter->v4_info,
 			.family = NFPROTO_IPV4
 		};
-		ratelimiter->v4_match->destroy(&dtor_v4);
-		module_put(ratelimiter->v4_match->me);
-		module_put(ratelimiter->v6_match->me);
+		v4_match->destroy(&dtor_v4);
 		return ret;
 	}
 #endif
@@ -97,18 +84,16 @@ void ratelimiter_uninit(struct ratelimiter *ratelimiter)
 {
 	struct xt_mtdtor_param dtor = { .net = ratelimiter->net };
 
-	dtor.match = ratelimiter->v4_match;
+	dtor.match = v4_match;
 	dtor.matchinfo = &ratelimiter->v4_info;
 	dtor.family = NFPROTO_IPV4;
-	ratelimiter->v4_match->destroy(&dtor);
-	module_put(ratelimiter->v4_match->me);
+	v4_match->destroy(&dtor);
 
 #if IS_ENABLED(CONFIG_IPV6)
-	dtor.match = ratelimiter->v6_match;
+	dtor.match = v6_match;
 	dtor.matchinfo = &ratelimiter->v6_info;
 	dtor.family = NFPROTO_IPV6;
-	ratelimiter->v6_match->destroy(&dtor);
-	module_put(ratelimiter->v6_match->me);
+	v6_match->destroy(&dtor);
 #endif
 }
 
@@ -118,14 +103,14 @@ bool ratelimiter_allow(struct ratelimiter *ratelimiter, struct sk_buff *skb)
 	if (unlikely(skb->len < sizeof(struct iphdr)))
 		return false;
 	if (ip_hdr(skb)->version == 4) {
-		action.match = ratelimiter->v4_match;
+		action.match = v4_match;
 		action.matchinfo = &ratelimiter->v4_info;
 		action.thoff = ip_hdrlen(skb);
 		action.family = NFPROTO_IPV4;
 	}
 #if IS_ENABLED(CONFIG_IPV6)
 	else if (ip_hdr(skb)->version == 6) {
-		action.match = ratelimiter->v6_match;
+		action.match = v6_match;
 		action.matchinfo = &ratelimiter->v6_info;
 		action.family = NFPROTO_IPV6;
 	}
@@ -134,3 +119,29 @@ bool ratelimiter_allow(struct ratelimiter *ratelimiter, struct sk_buff *skb)
 		return false;
 	return action.match->match(skb, &action);
 }
+
+int ratelimiter_module_init(void)
+{
+	v4_match = xt_request_find_match(NFPROTO_IPV4, "hashlimit", 1);
+	if (IS_ERR(v4_match)) {
+		pr_err("The xt_hashlimit module for IPv4 is required");
+		return PTR_ERR(v4_match);
+	}
+#if IS_ENABLED(CONFIG_IPV6)
+	v6_match = xt_request_find_match(NFPROTO_IPV6, "hashlimit", 1);
+	if (IS_ERR(v6_match)) {
+		pr_err("The xt_hashlimit module for IPv6 is required");
+		module_put(v4_match->me);
+		return PTR_ERR(v6_match);
+	}
+#endif
+	return 0;
+}
+
+void ratelimiter_module_deinit(void)
+{
+	module_put(v4_match->me);
+#if IS_ENABLED(CONFIG_IPV6)
+	module_put(v6_match->me);
+#endif
+}
-- 
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