l2tp: convert l2tp_tunnel_list to idr

[ Upstream commit c4d48a58f32c5972174a1d01c33b296fe378cce0 ]

l2tp uses l2tp_tunnel_list to track all registered tunnels and
to allocate tunnel ID's. IDR can do the same job.

More importantly, with IDR we can hold the ID before a successful
registration so that we don't need to worry about late error
handling, it is not easy to rollback socket changes.

This is a preparation for the following fix.

Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Guillaume Nault <gnault@redhat.com>
Cc: Jakub Sitnicki <jakub@cloudflare.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Tom Parkin <tparkin@katalix.com>
Signed-off-by: Cong Wang <cong.wang@bytedance.com>
Reviewed-by: Guillaume Nault <gnault@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Stable-dep-of: 0b2c59720e65 ("l2tp: close all race conditions in l2tp_tunnel_register()")
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index d22dbd9..68d8b2a 100644 (file)
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -104,9 +104,9 @@ static struct workqueue_struct *l2tp_wq;
 /* per-net private data for this module */
 static unsigned int l2tp_net_id;
 struct l2tp_net {
-       struct list_head l2tp_tunnel_list;
-       /* Lock for write access to l2tp_tunnel_list */
-       spinlock_t l2tp_tunnel_list_lock;
+       /* Lock for write access to l2tp_tunnel_idr */
+       spinlock_t l2tp_tunnel_idr_lock;
+       struct idr l2tp_tunnel_idr;
        struct hlist_head l2tp_session_hlist[L2TP_HASH_SIZE_2];
        /* Lock for write access to l2tp_session_hlist */
        spinlock_t l2tp_session_hlist_lock;
@@ -208,13 +208,10 @@ struct l2tp_tunnel *l2tp_tunnel_get(const struct net *net, u32 tunnel_id)
        struct l2tp_tunnel *tunnel;
 
        rcu_read_lock_bh();
-       list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
-               if (tunnel->tunnel_id == tunnel_id &&
-                   refcount_inc_not_zero(&tunnel->ref_count)) {
-                       rcu_read_unlock_bh();
-
-                       return tunnel;
-               }
+       tunnel = idr_find(&pn->l2tp_tunnel_idr, tunnel_id);
+       if (tunnel && refcount_inc_not_zero(&tunnel->ref_count)) {
+               rcu_read_unlock_bh();
+               return tunnel;
        }
        rcu_read_unlock_bh();
 
@@ -224,13 +221,14 @@ EXPORT_SYMBOL_GPL(l2tp_tunnel_get);
 
 struct l2tp_tunnel *l2tp_tunnel_get_nth(const struct net *net, int nth)
 {
-       const struct l2tp_net *pn = l2tp_pernet(net);
+       struct l2tp_net *pn = l2tp_pernet(net);
+       unsigned long tunnel_id, tmp;
        struct l2tp_tunnel *tunnel;
        int count = 0;
 
        rcu_read_lock_bh();
-       list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
-               if (++count > nth &&
+       idr_for_each_entry_ul(&pn->l2tp_tunnel_idr, tunnel, tmp, tunnel_id) {
+               if (tunnel && ++count > nth &&
                    refcount_inc_not_zero(&tunnel->ref_count)) {
                        rcu_read_unlock_bh();
                        return tunnel;
@@ -1229,6 +1227,15 @@ static void l2tp_udp_encap_destroy(struct sock *sk)
                l2tp_tunnel_delete(tunnel);
 }
 
+static void l2tp_tunnel_remove(struct net *net, struct l2tp_tunnel *tunnel)
+{
+       struct l2tp_net *pn = l2tp_pernet(net);
+
+       spin_lock_bh(&pn->l2tp_tunnel_idr_lock);
+       idr_remove(&pn->l2tp_tunnel_idr, tunnel->tunnel_id);
+       spin_unlock_bh(&pn->l2tp_tunnel_idr_lock);
+}
+
 /* Workqueue tunnel deletion function */
 static void l2tp_tunnel_del_work(struct work_struct *work)
 {
@@ -1236,7 +1243,6 @@ static void l2tp_tunnel_del_work(struct work_struct *work)
                                                  del_work);
        struct sock *sk = tunnel->sock;
        struct socket *sock = sk->sk_socket;
-       struct l2tp_net *pn;
 
        l2tp_tunnel_closeall(tunnel);
 
@@ -1250,12 +1256,7 @@ static void l2tp_tunnel_del_work(struct work_struct *work)
                }
        }
 
-       /* Remove the tunnel struct from the tunnel list */
-       pn = l2tp_pernet(tunnel->l2tp_net);
-       spin_lock_bh(&pn->l2tp_tunnel_list_lock);
-       list_del_rcu(&tunnel->list);
-       spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
-
+       l2tp_tunnel_remove(tunnel->l2tp_net, tunnel);
        /* drop initial ref */
        l2tp_tunnel_dec_refcount(tunnel);
 
@@ -1457,12 +1458,19 @@ static int l2tp_validate_socket(const struct sock *sk, const struct net *net,
 int l2tp_tunnel_register(struct l2tp_tunnel *tunnel, struct net *net,
                         struct l2tp_tunnel_cfg *cfg)
 {
-       struct l2tp_tunnel *tunnel_walk;
-       struct l2tp_net *pn;
+       struct l2tp_net *pn = l2tp_pernet(net);
+       u32 tunnel_id = tunnel->tunnel_id;
        struct socket *sock;
        struct sock *sk;
        int ret;
 
+       spin_lock_bh(&pn->l2tp_tunnel_idr_lock);
+       ret = idr_alloc_u32(&pn->l2tp_tunnel_idr, NULL, &tunnel_id, tunnel_id,
+                           GFP_ATOMIC);
+       spin_unlock_bh(&pn->l2tp_tunnel_idr_lock);
+       if (ret)
+               return ret == -ENOSPC ? -EEXIST : ret;
+
        if (tunnel->fd < 0) {
                ret = l2tp_tunnel_sock_create(net, tunnel->tunnel_id,
                                              tunnel->peer_tunnel_id, cfg,
@@ -1483,23 +1491,13 @@ int l2tp_tunnel_register(struct l2tp_tunnel *tunnel, struct net *net,
        rcu_assign_sk_user_data(sk, tunnel);
        write_unlock_bh(&sk->sk_callback_lock);
 
-       tunnel->l2tp_net = net;
-       pn = l2tp_pernet(net);
-
        sock_hold(sk);
        tunnel->sock = sk;
+       tunnel->l2tp_net = net;
 
-       spin_lock_bh(&pn->l2tp_tunnel_list_lock);
-       list_for_each_entry(tunnel_walk, &pn->l2tp_tunnel_list, list) {
-               if (tunnel_walk->tunnel_id == tunnel->tunnel_id) {
-                       spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
-                       sock_put(sk);
-                       ret = -EEXIST;
-                       goto err_sock;
-               }
-       }
-       list_add_rcu(&tunnel->list, &pn->l2tp_tunnel_list);
-       spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
+       spin_lock_bh(&pn->l2tp_tunnel_idr_lock);
+       idr_replace(&pn->l2tp_tunnel_idr, tunnel, tunnel->tunnel_id);
+       spin_unlock_bh(&pn->l2tp_tunnel_idr_lock);
 
        if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
                struct udp_tunnel_sock_cfg udp_cfg = {
@@ -1525,9 +1523,6 @@ int l2tp_tunnel_register(struct l2tp_tunnel *tunnel, struct net *net,
 
        return 0;
 
-err_sock:
-       write_lock_bh(&sk->sk_callback_lock);
-       rcu_assign_sk_user_data(sk, NULL);
 err_inval_sock:
        write_unlock_bh(&sk->sk_callback_lock);
 
@@ -1536,6 +1531,7 @@ err_inval_sock:
        else
                sockfd_put(sock);
 err:
+       l2tp_tunnel_remove(net, tunnel);
        return ret;
 }
 EXPORT_SYMBOL_GPL(l2tp_tunnel_register);
@@ -1649,8 +1645,8 @@ static __net_init int l2tp_init_net(struct net *net)
        struct l2tp_net *pn = net_generic(net, l2tp_net_id);
        int hash;
 
-       INIT_LIST_HEAD(&pn->l2tp_tunnel_list);
-       spin_lock_init(&pn->l2tp_tunnel_list_lock);
+       idr_init(&pn->l2tp_tunnel_idr);
+       spin_lock_init(&pn->l2tp_tunnel_idr_lock);
 
        for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++)
                INIT_HLIST_HEAD(&pn->l2tp_session_hlist[hash]);
@@ -1664,11 +1660,13 @@ static __net_exit void l2tp_exit_net(struct net *net)
 {
        struct l2tp_net *pn = l2tp_pernet(net);
        struct l2tp_tunnel *tunnel = NULL;
+       unsigned long tunnel_id, tmp;
        int hash;
 
        rcu_read_lock_bh();
-       list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
-               l2tp_tunnel_delete(tunnel);
+       idr_for_each_entry_ul(&pn->l2tp_tunnel_idr, tunnel, tmp, tunnel_id) {
+               if (tunnel)
+                       l2tp_tunnel_delete(tunnel);
        }
        rcu_read_unlock_bh();
 
@@ -1678,6 +1676,7 @@ static __net_exit void l2tp_exit_net(struct net *net)
 
        for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++)
                WARN_ON_ONCE(!hlist_empty(&pn->l2tp_session_hlist[hash]));
+       idr_destroy(&pn->l2tp_tunnel_idr);
 }
 
 static struct pernet_operations l2tp_net_ops = {