Included fixes:

* use rcu_dereference_bh() instead of rcu_access_pointer() where the
   pointer is actually dereferenced
 * ensure TCP global variables are initialized before they can be
   accessed via netlink (e.g. when attaching a TCP socket)
 * actually disable IPv4 redirects on multipeer interfaces (the
   previous attempt was a no-op and did not survive netns moves)
 * hash a floated peer by its transport identity only, consistently
   with the add and lookup paths
 * zero the sockaddr padding before learning a floated endpoint so it
   does not leak into the by_transp_addr hash key
 * ensure the socket is owned by ovpn before dereferencing
   sk_user_data
 * rehash a peer in the by_transp_addr table when its remote endpoint
   is updated via CMD_PEER_SET
 * avoid re-adding to the hashtables a peer that was concurrently
   removed (use-after-free)
 * limit keepalive values to one day to avoid overflowing the
   delayed-work delay on 32-bit systems
 * add the missing rtnl_link_ops->get_size callback so link messages
   account for the nested mode attribute
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Merge tag 'ovpn-net-20260730' of https://github.com/OpenVPN/ovpn-net-next

Antonio Quartulli says:

====================
Included fixes:

* use rcu_dereference_bh() instead of rcu_access_pointer() where the
  pointer is actually dereferenced
* ensure TCP global variables are initialized before they can be
  accessed via netlink (e.g. when attaching a TCP socket)
* actually disable IPv4 redirects on multipeer interfaces (the
  previous attempt was a no-op and did not survive netns moves)
* hash a floated peer by its transport identity only, consistently
  with the add and lookup paths
* zero the sockaddr padding before learning a floated endpoint so it
  does not leak into the by_transp_addr hash key
* ensure the socket is owned by ovpn before dereferencing
  sk_user_data
* rehash a peer in the by_transp_addr table when its remote endpoint
  is updated via CMD_PEER_SET
* avoid re-adding to the hashtables a peer that was concurrently
  removed (use-after-free)
* limit keepalive values to one day to avoid overflowing the
  delayed-work delay on 32-bit systems
* add the missing rtnl_link_ops->get_size callback so link messages
  account for the nested mode attribute

* tag 'ovpn-net-20260730' of https://github.com/OpenVPN/ovpn-net-next:
  ovpn: fix incorrect use of rcu_access_pointer()
  ovpn: ensure TCP vars are initialized first
  ovpn: disable IPv4 redirects on MP interfaces
  ovpn: hash floated peer by transport identity only
  ovpn: zero-initialize sockaddr before learning a floated endpoint
  ovpn: ensure socket is owned by ovpn before deref sk_user_data
  ovpn: rehash peer in by_transp_addr table on CMD_PEER_SET
  ovpn: skip rehash for peers already removed from by_id
  ovpn: limit keepalive values to one day
  ovpn: add missing rtnl_link_ops->get_size callback
====================

Link: https://patch.msgid.link/20260730094624.4102963-1-antonio@openvpn.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/netlink/specs/ovpn.yaml

@@ -118,12 +118,16 @@ attribute-sets:
         doc: >-
           The number of seconds after which a keep alive message is sent to the
           peer
+        checks:
+          max: 86400
       -
         name: keepalive-timeout
         type: u32
         doc: >-
           The number of seconds from the last activity after which the peer is
           assumed dead
+        checks:
+          max: 86400
       -
         name: del-reason
         type: u32

drivers/net/ovpn/main.c

@@ -35,25 +35,11 @@ static void ovpn_priv_free(struct net_device *net)
 
 static int ovpn_mp_alloc(struct ovpn_priv *ovpn)
 {
-	struct in_device *dev_v4;
 	int i;
 
 	if (ovpn->mode != OVPN_MODE_MP)
 		return 0;
 
-	dev_v4 = __in_dev_get_rtnl(ovpn->dev);
-	if (dev_v4) {
-		/* disable redirects as Linux gets confused by ovpn
-		 * handling same-LAN routing.
-		 * This happens because a multipeer interface is used as
-		 * relay point between hosts in the same subnet, while
-		 * in a classic LAN this would not be needed because the
-		 * two hosts would be able to talk directly.
-		 */
-		IN_DEV_CONF_SET(dev_v4, SEND_REDIRECTS, false);
-		IPV4_DEVCONF_ALL(dev_net(ovpn->dev), SEND_REDIRECTS) = false;
-	}
-
 	/* the peer container is fairly large, therefore we allocate it only in
 	 * MP mode
 	 */
@@ -97,9 +83,38 @@ static void ovpn_net_uninit(struct net_device *dev)
 	gro_cells_destroy(&ovpn->gro_cells);
 }
 
+static int ovpn_net_open(struct net_device *dev)
+{
+	struct ovpn_priv *ovpn = netdev_priv(dev);
+	struct in_device *dev_v4;
+
+	/* the IPv4 in_device (and thus its config) is recreated whenever the
+	 * interface is moved to a new netns, so redirects must be disabled on
+	 * every bring-up rather than once at creation time, otherwise the
+	 * setting is silently lost after such a move
+	 */
+	if (ovpn->mode == OVPN_MODE_MP) {
+		dev_v4 = __in_dev_get_rtnl(dev);
+		if (dev_v4) {
+			/* disable redirects as Linux gets confused by ovpn
+			 * handling same-LAN routing.
+			 * This happens because a multipeer interface is used as
+			 * relay point between hosts in the same subnet, while
+			 * in a classic LAN this would not be needed because the
+			 * two hosts would be able to talk directly.
+			 */
+			IN_DEV_CONF_SET(dev_v4, SEND_REDIRECTS, false);
+			IPV4_DEVCONF_ALL(dev_net(dev), SEND_REDIRECTS) = false;
+		}
+	}
+
+	return 0;
+}
+
 static const struct net_device_ops ovpn_netdev_ops = {
 	.ndo_init		= ovpn_net_init,
 	.ndo_uninit		= ovpn_net_uninit,
+	.ndo_open		= ovpn_net_open,
 	.ndo_start_xmit		= ovpn_net_xmit,
 };
 
@@ -183,6 +198,7 @@ static int ovpn_newlink(struct net_device *dev,
 	struct ovpn_priv *ovpn = netdev_priv(dev);
 	struct nlattr **data = params->data;
 	enum ovpn_mode mode = OVPN_MODE_P2P;
+	int ret;
 
 	if (data && data[IFLA_OVPN_MODE]) {
 		mode = nla_get_u8(data[IFLA_OVPN_MODE]);
@@ -207,7 +223,17 @@ static int ovpn_newlink(struct net_device *dev,
 	else
 		netif_carrier_off(dev);
 
-	return register_netdevice(dev);
+	ret = register_netdevice(dev);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+
+static size_t ovpn_get_size(const struct net_device *dev)
+{
+	/* IFLA_OVPN_MODE */
+	return nla_total_size(sizeof(u8));
 }
 
 static int ovpn_fill_info(struct sk_buff *skb, const struct net_device *dev)
@@ -228,13 +254,17 @@ static struct rtnl_link_ops ovpn_link_ops = {
 	.policy = ovpn_policy,
 	.maxtype = IFLA_OVPN_MAX,
 	.newlink = ovpn_newlink,
+	.get_size = ovpn_get_size,
 	.fill_info = ovpn_fill_info,
 };
 
 static int __init ovpn_init(void)
 {
-	int err = rtnl_link_register(&ovpn_link_ops);
+	int err;
 
+	ovpn_tcp_init();
+
+	err = rtnl_link_register(&ovpn_link_ops);
 	if (err) {
 		pr_err("ovpn: can't register rtnl link ops: %d\n", err);
 		return err;
@@ -246,8 +276,6 @@ static int __init ovpn_init(void)
 		goto unreg_rtnl;
 	}
 
-	ovpn_tcp_init();
-
 	return 0;
 
 unreg_rtnl:

drivers/net/ovpn/netlink-gen.c

@@ -16,6 +16,14 @@ static const struct netlink_range_validation ovpn_a_peer_id_range = {
 	.max	= 16777215ULL,
 };
 
+static const struct netlink_range_validation ovpn_a_peer_keepalive_interval_range = {
+	.max	= 86400ULL,
+};
+
+static const struct netlink_range_validation ovpn_a_peer_keepalive_timeout_range = {
+	.max	= 86400ULL,
+};
+
 static const struct netlink_range_validation ovpn_a_peer_tx_id_range = {
 	.max	= 16777215ULL,
 };
@@ -68,8 +76,8 @@ const struct nla_policy ovpn_peer_nl_policy[OVPN_A_PEER_TX_ID + 1] = {
 	[OVPN_A_PEER_LOCAL_IPV4] = { .type = NLA_BE32, },
 	[OVPN_A_PEER_LOCAL_IPV6] = NLA_POLICY_EXACT_LEN(16),
 	[OVPN_A_PEER_LOCAL_PORT] = NLA_POLICY_MIN(NLA_BE16, 1),
-	[OVPN_A_PEER_KEEPALIVE_INTERVAL] = { .type = NLA_U32, },
-	[OVPN_A_PEER_KEEPALIVE_TIMEOUT] = { .type = NLA_U32, },
+	[OVPN_A_PEER_KEEPALIVE_INTERVAL] = NLA_POLICY_FULL_RANGE(NLA_U32, &ovpn_a_peer_keepalive_interval_range),
+	[OVPN_A_PEER_KEEPALIVE_TIMEOUT] = NLA_POLICY_FULL_RANGE(NLA_U32, &ovpn_a_peer_keepalive_timeout_range),
 	[OVPN_A_PEER_DEL_REASON] = NLA_POLICY_MAX(NLA_U32, 4),
 	[OVPN_A_PEER_VPN_RX_BYTES] = { .type = NLA_UINT, },
 	[OVPN_A_PEER_VPN_TX_BYTES] = { .type = NLA_UINT, },
@@ -97,8 +105,8 @@ const struct nla_policy ovpn_peer_new_input_nl_policy[OVPN_A_PEER_TX_ID + 1] = {
 	[OVPN_A_PEER_VPN_IPV6] = NLA_POLICY_EXACT_LEN(16),
 	[OVPN_A_PEER_LOCAL_IPV4] = { .type = NLA_BE32, },
 	[OVPN_A_PEER_LOCAL_IPV6] = NLA_POLICY_EXACT_LEN(16),
-	[OVPN_A_PEER_KEEPALIVE_INTERVAL] = { .type = NLA_U32, },
-	[OVPN_A_PEER_KEEPALIVE_TIMEOUT] = { .type = NLA_U32, },
+	[OVPN_A_PEER_KEEPALIVE_INTERVAL] = NLA_POLICY_FULL_RANGE(NLA_U32, &ovpn_a_peer_keepalive_interval_range),
+	[OVPN_A_PEER_KEEPALIVE_TIMEOUT] = NLA_POLICY_FULL_RANGE(NLA_U32, &ovpn_a_peer_keepalive_timeout_range),
 	[OVPN_A_PEER_TX_ID] = NLA_POLICY_FULL_RANGE(NLA_U32, &ovpn_a_peer_tx_id_range),
 };
 
@@ -112,8 +120,8 @@ const struct nla_policy ovpn_peer_set_input_nl_policy[OVPN_A_PEER_TX_ID + 1] = {
 	[OVPN_A_PEER_VPN_IPV6] = NLA_POLICY_EXACT_LEN(16),
 	[OVPN_A_PEER_LOCAL_IPV4] = { .type = NLA_BE32, },
 	[OVPN_A_PEER_LOCAL_IPV6] = NLA_POLICY_EXACT_LEN(16),
-	[OVPN_A_PEER_KEEPALIVE_INTERVAL] = { .type = NLA_U32, },
-	[OVPN_A_PEER_KEEPALIVE_TIMEOUT] = { .type = NLA_U32, },
+	[OVPN_A_PEER_KEEPALIVE_INTERVAL] = NLA_POLICY_FULL_RANGE(NLA_U32, &ovpn_a_peer_keepalive_interval_range),
+	[OVPN_A_PEER_KEEPALIVE_TIMEOUT] = NLA_POLICY_FULL_RANGE(NLA_U32, &ovpn_a_peer_keepalive_timeout_range),
 	[OVPN_A_PEER_TX_ID] = NLA_POLICY_FULL_RANGE(NLA_U32, &ovpn_a_peer_tx_id_range),
 };
 

drivers/net/ovpn/netlink.c

@@ -534,6 +534,12 @@ int ovpn_nl_peer_set_doit(struct sk_buff *skb, struct genl_info *info)
 	 */
 	if (ret > 0)
 		ovpn_peer_hash_vpn_ip(peer);
+	/* if the remote endpoint was updated, the by_transp_addr hash bucket
+	 * also needs to be refreshed, otherwise incoming packets from the new
+	 * remote address would fail the lockless lookup
+	 */
+	if (attrs[OVPN_A_PEER_REMOTE_IPV4] || attrs[OVPN_A_PEER_REMOTE_IPV6])
+		ovpn_peer_hash_transp_addr(peer);
 	spin_unlock_bh(&ovpn->lock);
 	ovpn_peer_put(peer);
 

drivers/net/ovpn/peer.c

@@ -189,6 +189,9 @@ int ovpn_peer_reset_sockaddr(struct ovpn_peer *peer,
 	&(*__tbl1)[ovpn_get_hash_slot(*__tbl1, _key, _key_len)];\
 })
 
+static void __ovpn_peer_hash_transp_addr(struct ovpn_peer *peer,
+					 const struct ovpn_bind *bind);
+
 /**
  * ovpn_peer_endpoints_update - update remote or local endpoint for peer
  * @peer: peer to update the remote endpoint for
@@ -196,7 +199,6 @@ int ovpn_peer_reset_sockaddr(struct ovpn_peer *peer,
  */
 void ovpn_peer_endpoints_update(struct ovpn_peer *peer, struct sk_buff *skb)
 {
-	struct hlist_nulls_head *nhead;
 	struct sockaddr_storage ss;
 	struct sockaddr_in6 *sa6;
 	bool reset_cache = false;
@@ -220,9 +222,16 @@ void ovpn_peer_endpoints_update(struct ovpn_peer *peer, struct sk_buff *skb)
 			 */
 			local_ip = &ip_hdr(skb)->daddr;
 			sa = (struct sockaddr_in *)&ss;
-			sa->sin_family = AF_INET;
-			sa->sin_addr.s_addr = ip_hdr(skb)->saddr;
-			sa->sin_port = udp_hdr(skb)->source;
+			/* use a designated initializer so the sin_zero padding
+			 * is zeroed (it ends up in the by_transp_addr hash key)
+			 * without memset-ing the whole sockaddr_storage on the
+			 * RX fast path
+			 */
+			*sa = (struct sockaddr_in) {
+				.sin_family = AF_INET,
+				.sin_addr.s_addr = ip_hdr(skb)->saddr,
+				.sin_port = udp_hdr(skb)->source,
+			};
 			salen = sizeof(*sa);
 			reset_cache = true;
 			break;
@@ -248,11 +257,19 @@ void ovpn_peer_endpoints_update(struct ovpn_peer *peer, struct sk_buff *skb)
 			 */
 			local_ip = &ipv6_hdr(skb)->daddr;
 			sa6 = (struct sockaddr_in6 *)&ss;
-			sa6->sin6_family = AF_INET6;
-			sa6->sin6_addr = ipv6_hdr(skb)->saddr;
-			sa6->sin6_port = udp_hdr(skb)->source;
-			sa6->sin6_scope_id = ipv6_iface_scope_id(&ipv6_hdr(skb)->saddr,
-								 skb->skb_iif);
+			/* use a designated initializer so the sin6_flowinfo
+			 * padding is zeroed (it ends up in the by_transp_addr
+			 * hash key) without memset-ing the whole
+			 * sockaddr_storage on the RX fast path
+			 */
+			*sa6 = (struct sockaddr_in6) {
+				.sin6_family = AF_INET6,
+				.sin6_addr = ipv6_hdr(skb)->saddr,
+				.sin6_port = udp_hdr(skb)->source,
+				.sin6_scope_id =
+					ipv6_iface_scope_id(&ipv6_hdr(skb)->saddr,
+							    skb->skb_iif),
+			};
 			salen = sizeof(*sa6);
 			reset_cache = true;
 			break;
@@ -295,42 +312,25 @@ void ovpn_peer_endpoints_update(struct ovpn_peer *peer, struct sk_buff *skb)
 	ovpn_nl_peer_float_notify(peer, &ss);
 
 	/* rehashing is required only in MP mode as P2P has one peer
-	 * only and thus there is no hashtable
+	 * only and thus there is no hashtable.
+	 *
+	 * This function may be invoked concurrently, so re-read peer->bind
+	 * under the proper locks and rehash against its current value.
 	 */
-	if (peer->ovpn->mode == OVPN_MODE_MP) {
-		spin_lock_bh(&peer->ovpn->lock);
-		spin_lock_bh(&peer->lock);
-		bind = rcu_dereference_protected(peer->bind,
-						 lockdep_is_held(&peer->lock));
-		if (unlikely(!bind)) {
-			spin_unlock_bh(&peer->lock);
-			spin_unlock_bh(&peer->ovpn->lock);
-			return;
-		}
+	if (peer->ovpn->mode != OVPN_MODE_MP)
+		return;
 
-		/* This function may be invoked concurrently, therefore another
-		 * float may have happened in parallel: perform rehashing
-		 * using the peer->bind->remote directly as key
-		 */
-
-		switch (bind->remote.in4.sin_family) {
-		case AF_INET:
-			salen = sizeof(*sa);
-			break;
-		case AF_INET6:
-			salen = sizeof(*sa6);
-			break;
-		}
-
-		/* remove old hashing */
-		hlist_nulls_del_init_rcu(&peer->hash_entry_transp_addr);
-		/* re-add with new transport address */
-		nhead = ovpn_get_hash_head(peer->ovpn->peers->by_transp_addr,
-					   &bind->remote, salen);
-		hlist_nulls_add_head_rcu(&peer->hash_entry_transp_addr, nhead);
-		spin_unlock_bh(&peer->lock);
-		spin_unlock_bh(&peer->ovpn->lock);
-	}
+	/* This function may be invoked concurrently, therefore another
+	 * float may have happened in parallel: re-acquire the locks and
+	 * rehash using the peer->bind->remote directly as key
+	 */
+	spin_lock_bh(&peer->ovpn->lock);
+	spin_lock_bh(&peer->lock);
+	bind = rcu_dereference_protected(peer->bind,
+					 lockdep_is_held(&peer->lock));
+	__ovpn_peer_hash_transp_addr(peer, bind);
+	spin_unlock_bh(&peer->lock);
+	spin_unlock_bh(&peer->ovpn->lock);
 	return;
 unlock:
 	spin_unlock_bh(&peer->lock);
@@ -896,6 +896,83 @@ bool ovpn_peer_check_by_src(struct ovpn_priv *ovpn, struct sk_buff *skb,
 	return match;
 }
 
+/* Move @peer to the by_transp_addr bucket matching its current bind.
+ *
+ * Caller must hold both peer->ovpn->lock and peer->lock, and must have
+ * already dereferenced a valid (non-NULL) peer->bind, passed in as @bind.
+ */
+static void __ovpn_peer_hash_transp_addr(struct ovpn_peer *peer,
+					 const struct ovpn_bind *bind)
+{
+	struct sockaddr_storage sa = {};
+	struct hlist_nulls_head *nhead;
+	struct sockaddr_in6 *sa6;
+	struct sockaddr_in *sa4;
+	size_t salen;
+
+	lockdep_assert_held(&peer->ovpn->lock);
+	lockdep_assert_held(&peer->lock);
+
+	if (WARN_ON_ONCE(!bind))
+		return;
+
+	/* peer may have been concurrently removed between the caller's
+	 * initial lookup and our acquisition of ovpn->lock; skip the
+	 * rehash so we don't re-insert a removed peer
+	 */
+	if (unlikely(hlist_unhashed(&peer->hash_entry_id)))
+		return;
+
+	/* Build the hash key from the transport identity only
+	 * (family/address/port), matching ovpn_peer_add_mp() and the lookup
+	 * in ovpn_peer_get_by_transp_addr(). Hashing bind->remote directly
+	 * would fold in sin6_scope_id (set on the float path but never by the
+	 * lookup), scattering the peer into a bucket lookups cannot reach.
+	 */
+	switch (bind->remote.in4.sin_family) {
+	case AF_INET:
+		sa4 = (struct sockaddr_in *)&sa;
+		sa4->sin_family = AF_INET;
+		sa4->sin_addr.s_addr = bind->remote.in4.sin_addr.s_addr;
+		sa4->sin_port = bind->remote.in4.sin_port;
+		salen = sizeof(*sa4);
+		break;
+	case AF_INET6:
+		sa6 = (struct sockaddr_in6 *)&sa;
+		sa6->sin6_family = AF_INET6;
+		sa6->sin6_addr = bind->remote.in6.sin6_addr;
+		sa6->sin6_port = bind->remote.in6.sin6_port;
+		salen = sizeof(*sa6);
+		break;
+	default:
+		return;
+	}
+
+	/* remove old hashing (no-op if entry is not currently linked) */
+	hlist_nulls_del_init_rcu(&peer->hash_entry_transp_addr);
+	/* re-add with current transport address */
+	nhead = ovpn_get_hash_head(peer->ovpn->peers->by_transp_addr, &sa,
+				   salen);
+	hlist_nulls_add_head_rcu(&peer->hash_entry_transp_addr, nhead);
+}
+
+void ovpn_peer_hash_transp_addr(struct ovpn_peer *peer)
+{
+	struct ovpn_bind *bind;
+
+	lockdep_assert_held(&peer->ovpn->lock);
+
+	/* rehashing makes sense only in multipeer mode */
+	if (peer->ovpn->mode != OVPN_MODE_MP)
+		return;
+
+	spin_lock_bh(&peer->lock);
+	bind = rcu_dereference_protected(peer->bind,
+					 lockdep_is_held(&peer->lock));
+	__ovpn_peer_hash_transp_addr(peer, bind);
+	spin_unlock_bh(&peer->lock);
+}
+
 void ovpn_peer_hash_vpn_ip(struct ovpn_peer *peer)
 {
 	struct hlist_nulls_head *nhead;
@@ -906,6 +983,13 @@ void ovpn_peer_hash_vpn_ip(struct ovpn_peer *peer)
 	if (peer->ovpn->mode != OVPN_MODE_MP)
 		return;
 
+	/* peer may have been concurrently removed between the caller's
+	 * initial lookup and our acquisition of ovpn->lock; skip the
+	 * rehash so we don't re-insert a removed peer
+	 */
+	if (hlist_unhashed(&peer->hash_entry_id))
+		return;
+
 	if (peer->vpn_addrs.ipv4.s_addr != htonl(INADDR_ANY)) {
 		/* remove potential old hashing */
 		hlist_nulls_del_init_rcu(&peer->hash_entry_addr4);
@@ -1165,7 +1249,7 @@ static void ovpn_peer_release_p2p(struct ovpn_priv *ovpn, struct sock *sk,
 	}
 
 	if (sk) {
-		ovpn_sock = rcu_access_pointer(peer->sock);
+		ovpn_sock = rcu_dereference_bh(peer->sock);
 		if (!ovpn_sock || ovpn_sock->sk != sk) {
 			spin_unlock_bh(&ovpn->lock);
 			return;

drivers/net/ovpn/peer.h

@@ -150,6 +150,7 @@ struct ovpn_peer *ovpn_peer_get_by_id(struct ovpn_priv *ovpn, u32 peer_id);
 struct ovpn_peer *ovpn_peer_get_by_dst(struct ovpn_priv *ovpn,
 				       struct sk_buff *skb);
 void ovpn_peer_hash_vpn_ip(struct ovpn_peer *peer);
+void ovpn_peer_hash_transp_addr(struct ovpn_peer *peer);
 bool ovpn_peer_check_by_src(struct ovpn_priv *ovpn, struct sk_buff *skb,
 			    struct ovpn_peer *peer);
 

drivers/net/ovpn/socket.c

@@ -162,6 +162,15 @@ struct ovpn_socket *ovpn_socket_new(struct socket *sock, struct ovpn_peer *peer)
 		rcu_read_lock();
 		ovpn_sock = rcu_dereference_sk_user_data(sk);
 		if (ovpn_sock) {
+			/* something else filled the sk_user_data without
+			 * setting the encap_type. Reject the socket.
+			 */
+			if (!type) {
+				ovpn_sock = ERR_PTR(-EBUSY);
+				rcu_read_unlock();
+				goto sock_release;
+			}
+
 			/* socket owned by another ovpn instance, we can't use it */
 			if (ovpn_sock->ovpn != peer->ovpn) {
 				ovpn_sock = ERR_PTR(-EBUSY);