mptcp: add netlink pm addr entry refcount

This patch adds netlink PM address entry refcount. Init 'refcont' of
every address entry to 1..

Increase this refcount counter when a subflow connecting or an address
signaling in mptcp_pm_create_subflow_or_signal_addr() and
fill_local_addresses_vec().

Decrease it in __mptcp_pm_release_addr_entry(). When the counter reaches
1, then free this entry.

Signed-off-by: Geliang Tang <[email protected]>

net/mptcp/pm_netlink.c

@@ -603,8 +603,10 @@ static void mptcp_pm_create_subflow_or_signal_addr(struct mptcp_sock *msk)
 			continue;
 
 		spin_unlock_bh(&msk->pm.lock);
-		for (i = 0; i < nr; i++)
-			__mptcp_subflow_connect(sk, &local->addr, &addrs[i]);
+		for (i = 0; i < nr; i++) {
+			if (refcount_inc_not_zero(&local->refcnt))
+				__mptcp_subflow_connect(sk, &local->addr, &addrs[i]);
+		}
 		spin_lock_bh(&msk->pm.lock);
 	}
 	mptcp_pm_nl_check_work_pending(msk);
@@ -644,7 +646,8 @@ static unsigned int fill_local_addresses_vec(struct mptcp_sock *msk,
 		if (!mptcp_pm_addr_families_match(sk, &entry->addr, remote))
 			continue;
 
-		if (msk->pm.subflows < subflows_max) {
+		if (msk->pm.subflows < subflows_max &&
+		    refcount_inc_not_zero(&entry->refcnt)) {
 			msk->pm.subflows++;
 			addrs[i++] = entry->addr;
 		}
@@ -895,9 +898,11 @@ static bool address_use_port(struct mptcp_pm_addr_entry *entry)
 /* caller must ensure the RCU grace period is already elapsed */
 static void __mptcp_pm_release_addr_entry(struct mptcp_pm_addr_entry *entry)
 {
-	if (entry->lsk)
-		sock_release(entry->lsk);
-	kfree(entry);
+	if (!refcount_dec_not_one(&entry->refcnt)) {
+		if (entry->lsk)
+			sock_release(entry->lsk);
+		kfree(entry);
+	}
 }
 
 static int mptcp_pm_nl_append_new_local_addr(struct pm_nl_pernet *pernet,
@@ -1087,6 +1092,7 @@ int mptcp_pm_nl_get_local_id(struct mptcp_sock *msk, struct mptcp_addr_info *skc
 	entry->ifindex = 0;
 	entry->flags = MPTCP_PM_ADDR_FLAG_IMPLICIT;
 	entry->lsk = NULL;
+	refcount_set(&entry->refcnt, 1);
 	ret = mptcp_pm_nl_append_new_local_addr(pernet, entry);
 	if (ret < 0)
 		kfree(entry);
@@ -1314,6 +1320,7 @@ int mptcp_pm_nl_add_addr_doit(struct sk_buff *skb, struct genl_info *info)
 	}
 
 	*entry = addr;
+	refcount_set(&entry->refcnt, 1);
 	if (entry->addr.port) {
 		ret = mptcp_pm_nl_create_listen_socket(skb->sk, entry);
 		if (ret) {