[net-next] tcp: md5: protects md5sig_info with RCU

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index c2025f1..115389e 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -463,7 +463,7 @@  struct tcp_sock {
 	const struct tcp_sock_af_ops	*af_specific;
 
 /* TCP MD5 Signature Option information */
-	struct tcp_md5sig_info	*md5sig_info;
+	struct tcp_md5sig_info	__rcu *md5sig_info;
 #endif
 
 	/* When the cookie options are generated and exchanged, then this
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 10ae4c7..78880ba 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1150,6 +1150,7 @@  struct tcp_md5sig_key {
 /* - sock block */
 struct tcp_md5sig_info {
 	struct hlist_head	head;
+	struct rcu_head		rcu;
 };
 
 /* - pseudo header */
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index da5d322..567cca9 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -879,14 +879,18 @@  struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk,
 	struct tcp_md5sig_key *key;
 	struct hlist_node *pos;
 	unsigned int size = sizeof(struct in_addr);
+	struct tcp_md5sig_info *md5sig;
 
-	if (!tp->md5sig_info)
+	/* caller either holds rcu_read_lock() or socket lock */
+	md5sig = rcu_dereference_check(tp->md5sig_info,
+				       sock_owned_by_user(sk));
+	if (!md5sig)
 		return NULL;
 #if IS_ENABLED(CONFIG_IPV6)
 	if (family == AF_INET6)
 		size = sizeof(struct in6_addr);
 #endif
-	hlist_for_each_entry_rcu(key, pos, &tp->md5sig_info->head, node) {
+	hlist_for_each_entry_rcu(key, pos, &md5sig->head, node) {
 		if (key->family != family)
 			continue;
 		if (!memcmp(&key->addr, addr, size))
@@ -932,7 +936,8 @@  int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
 		return 0;
 	}
 
-	md5sig = tp->md5sig_info;
+	md5sig = rcu_dereference_protected(tp->md5sig_info,
+					   sock_owned_by_user(sk));
 	if (!md5sig) {
 		md5sig = kmalloc(sizeof(*md5sig), gfp);
 		if (!md5sig)
@@ -940,7 +945,7 @@  int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
 
 		sk_nocaps_add(sk, NETIF_F_GSO_MASK);
 		INIT_HLIST_HEAD(&md5sig->head);
-		tp->md5sig_info = md5sig;
+		rcu_assign_pointer(tp->md5sig_info, md5sig);
 	}
 
 	key = sock_kmalloc(sk, sizeof(*key), gfp);
@@ -966,6 +971,7 @@  int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr, int family)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct tcp_md5sig_key *key;
+	struct tcp_md5sig_info *md5sig;
 
 	key = tcp_md5_do_lookup(sk, (union tcp_md5_addr *)&addr, AF_INET);
 	if (!key)
@@ -973,7 +979,9 @@  int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr, int family)
 	hlist_del_rcu(&key->node);
 	atomic_sub(sizeof(*key), &sk->sk_omem_alloc);
 	kfree_rcu(key, rcu);
-	if (hlist_empty(&tp->md5sig_info->head))
+	md5sig = rcu_dereference_protected(tp->md5sig_info,
+					   sock_owned_by_user(sk));
+	if (hlist_empty(&md5sig->head))
 		tcp_free_md5sig_pool();
 	return 0;
 }
@@ -984,10 +992,13 @@  void tcp_clear_md5_list(struct sock *sk)
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct tcp_md5sig_key *key;
 	struct hlist_node *pos, *n;
+	struct tcp_md5sig_info *md5sig;
 
-	if (!hlist_empty(&tp->md5sig_info->head))
+	md5sig = rcu_dereference_protected(tp->md5sig_info, 1);
+
+	if (!hlist_empty(&md5sig->head))
 		tcp_free_md5sig_pool();
-	hlist_for_each_entry_safe(key, pos, n, &tp->md5sig_info->head, node) {
+	hlist_for_each_entry_safe(key, pos, n, &md5sig->head, node) {
 		hlist_del_rcu(&key->node);
 		atomic_sub(sizeof(*key), &sk->sk_omem_alloc);
 		kfree_rcu(key, rcu);
@@ -1009,12 +1020,9 @@  static int tcp_v4_parse_md5_keys(struct sock *sk, char __user *optval,
 	if (sin->sin_family != AF_INET)
 		return -EINVAL;
 
-	if (!cmd.tcpm_key || !cmd.tcpm_keylen) {
-		if (!tcp_sk(sk)->md5sig_info)
-			return -ENOENT;
+	if (!cmd.tcpm_key || !cmd.tcpm_keylen)
 		return tcp_md5_do_del(sk, (union tcp_md5_addr *)&sin->sin_addr.s_addr,
 				      AF_INET);
-	}
 
 	if (cmd.tcpm_keylen > TCP_MD5SIG_MAXKEYLEN)
 		return -EINVAL;
@@ -1896,7 +1904,7 @@  void tcp_v4_destroy_sock(struct sock *sk)
 	/* Clean up the MD5 key list, if any */
 	if (tp->md5sig_info) {
 		tcp_clear_md5_list(sk);
-		kfree(tp->md5sig_info);
+		kfree_rcu(tp->md5sig_info, rcu);
 		tp->md5sig_info = NULL;
 	}
 #endif
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index bec41f9..c250181 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -571,8 +571,6 @@  static int tcp_v6_parse_md5_keys (struct sock *sk, char __user *optval,
 		return -EINVAL;
 
 	if (!cmd.tcpm_keylen) {
-		if (!tcp_sk(sk)->md5sig_info)
-			return -ENOENT;
 		if (ipv6_addr_v4mapped(&sin6->sin6_addr))
 			return tcp_md5_do_del(sk, (union tcp_md5_addr *)&sin6->sin6_addr.s6_addr32[3],
 					      AF_INET);