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authorDavid S. Miller <davem@davemloft.net>2018-04-11 17:41:28 -0400
committerDavid S. Miller <davem@davemloft.net>2018-04-11 17:41:28 -0400
commit0c84cee8f131a090f77f5a3dea5d6a7bd99c00db (patch)
treef616d85bc1fa0339fc227d4672cea1f4b4042a30
parent83c1f36f9880814b24cdf6c2f91f66f61db65326 (diff)
parentf6cd651b056ffd3b4e8496afd44d4ed44bf69136 (diff)
downloadlinux-0c84cee8f131a090f77f5a3dea5d6a7bd99c00db.tar.bz2
Merge branch 'l2tp-tunnel-creation-fixes'
Guillaume Nault says: ==================== l2tp: tunnel creation fixes L2TP tunnel creation is racy. We need to make sure that the tunnel returned by l2tp_tunnel_create() isn't going to be freed while the caller is using it. This is done in patch #1, by separating tunnel creation from tunnel registration. With the tunnel registration code in place, we can now check for duplicate tunnels in a race-free way. This is done in patch #2, which incidentally removes the last use of l2tp_tunnel_find(). ==================== Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/l2tp/l2tp_core.c225
-rw-r--r--net/l2tp/l2tp_core.h4
-rw-r--r--net/l2tp/l2tp_netlink.c22
-rw-r--r--net/l2tp/l2tp_ppp.c9
4 files changed, 123 insertions, 137 deletions
diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index 14b67dfacc4b..0fbd3ee26165 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -335,26 +335,6 @@ err_tlock:
}
EXPORT_SYMBOL_GPL(l2tp_session_register);
-/* Lookup a tunnel by id
- */
-struct l2tp_tunnel *l2tp_tunnel_find(const struct net *net, u32 tunnel_id)
-{
- struct l2tp_tunnel *tunnel;
- struct l2tp_net *pn = l2tp_pernet(net);
-
- rcu_read_lock_bh();
- list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {
- if (tunnel->tunnel_id == tunnel_id) {
- rcu_read_unlock_bh();
- return tunnel;
- }
- }
- rcu_read_unlock_bh();
-
- return NULL;
-}
-EXPORT_SYMBOL_GPL(l2tp_tunnel_find);
-
struct l2tp_tunnel *l2tp_tunnel_find_nth(const struct net *net, int nth)
{
struct l2tp_net *pn = l2tp_pernet(net);
@@ -1436,74 +1416,11 @@ int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id, u32
{
struct l2tp_tunnel *tunnel = NULL;
int err;
- struct socket *sock = NULL;
- struct sock *sk = NULL;
- struct l2tp_net *pn;
enum l2tp_encap_type encap = L2TP_ENCAPTYPE_UDP;
- /* Get the tunnel socket from the fd, which was opened by
- * the userspace L2TP daemon. If not specified, create a
- * kernel socket.
- */
- if (fd < 0) {
- err = l2tp_tunnel_sock_create(net, tunnel_id, peer_tunnel_id,
- cfg, &sock);
- if (err < 0)
- goto err;
- } else {
- sock = sockfd_lookup(fd, &err);
- if (!sock) {
- pr_err("tunl %u: sockfd_lookup(fd=%d) returned %d\n",
- tunnel_id, fd, err);
- err = -EBADF;
- goto err;
- }
-
- /* Reject namespace mismatches */
- if (!net_eq(sock_net(sock->sk), net)) {
- pr_err("tunl %u: netns mismatch\n", tunnel_id);
- err = -EINVAL;
- goto err;
- }
- }
-
- sk = sock->sk;
-
if (cfg != NULL)
encap = cfg->encap;
- /* Quick sanity checks */
- err = -EPROTONOSUPPORT;
- if (sk->sk_type != SOCK_DGRAM) {
- pr_debug("tunl %hu: fd %d wrong socket type\n",
- tunnel_id, fd);
- goto err;
- }
- switch (encap) {
- case L2TP_ENCAPTYPE_UDP:
- if (sk->sk_protocol != IPPROTO_UDP) {
- pr_err("tunl %hu: fd %d wrong protocol, got %d, expected %d\n",
- tunnel_id, fd, sk->sk_protocol, IPPROTO_UDP);
- goto err;
- }
- break;
- case L2TP_ENCAPTYPE_IP:
- if (sk->sk_protocol != IPPROTO_L2TP) {
- pr_err("tunl %hu: fd %d wrong protocol, got %d, expected %d\n",
- tunnel_id, fd, sk->sk_protocol, IPPROTO_L2TP);
- goto err;
- }
- break;
- }
-
- /* Check if this socket has already been prepped */
- tunnel = l2tp_tunnel(sk);
- if (tunnel != NULL) {
- /* This socket has already been prepped */
- err = -EBUSY;
- goto err;
- }
-
tunnel = kzalloc(sizeof(struct l2tp_tunnel), GFP_KERNEL);
if (tunnel == NULL) {
err = -ENOMEM;
@@ -1520,72 +1437,126 @@ int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id, u32
rwlock_init(&tunnel->hlist_lock);
tunnel->acpt_newsess = true;
- /* The net we belong to */
- tunnel->l2tp_net = net;
- pn = l2tp_pernet(net);
-
if (cfg != NULL)
tunnel->debug = cfg->debug;
- /* Mark socket as an encapsulation socket. See net/ipv4/udp.c */
tunnel->encap = encap;
- if (encap == L2TP_ENCAPTYPE_UDP) {
- struct udp_tunnel_sock_cfg udp_cfg = { };
-
- udp_cfg.sk_user_data = tunnel;
- udp_cfg.encap_type = UDP_ENCAP_L2TPINUDP;
- udp_cfg.encap_rcv = l2tp_udp_encap_recv;
- udp_cfg.encap_destroy = l2tp_udp_encap_destroy;
-
- setup_udp_tunnel_sock(net, sock, &udp_cfg);
- } else {
- sk->sk_user_data = tunnel;
- }
- /* Bump the reference count. The tunnel context is deleted
- * only when this drops to zero. A reference is also held on
- * the tunnel socket to ensure that it is not released while
- * the tunnel is extant. Must be done before sk_destruct is
- * set.
- */
refcount_set(&tunnel->ref_count, 1);
- sock_hold(sk);
- tunnel->sock = sk;
tunnel->fd = fd;
- /* Hook on the tunnel socket destructor so that we can cleanup
- * if the tunnel socket goes away.
- */
- tunnel->old_sk_destruct = sk->sk_destruct;
- sk->sk_destruct = &l2tp_tunnel_destruct;
- lockdep_set_class_and_name(&sk->sk_lock.slock, &l2tp_socket_class, "l2tp_sock");
-
- sk->sk_allocation = GFP_ATOMIC;
-
/* Init delete workqueue struct */
INIT_WORK(&tunnel->del_work, l2tp_tunnel_del_work);
- /* Add tunnel to our list */
INIT_LIST_HEAD(&tunnel->list);
- spin_lock_bh(&pn->l2tp_tunnel_list_lock);
- list_add_rcu(&tunnel->list, &pn->l2tp_tunnel_list);
- spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
err = 0;
err:
if (tunnelp)
*tunnelp = tunnel;
- /* If tunnel's socket was created by the kernel, it doesn't
- * have a file.
- */
- if (sock && sock->file)
- sockfd_put(sock);
-
return err;
}
EXPORT_SYMBOL_GPL(l2tp_tunnel_create);
+static int l2tp_validate_socket(const struct sock *sk, const struct net *net,
+ enum l2tp_encap_type encap)
+{
+ if (!net_eq(sock_net(sk), net))
+ return -EINVAL;
+
+ if (sk->sk_type != SOCK_DGRAM)
+ return -EPROTONOSUPPORT;
+
+ if ((encap == L2TP_ENCAPTYPE_UDP && sk->sk_protocol != IPPROTO_UDP) ||
+ (encap == L2TP_ENCAPTYPE_IP && sk->sk_protocol != IPPROTO_L2TP))
+ return -EPROTONOSUPPORT;
+
+ if (sk->sk_user_data)
+ return -EBUSY;
+
+ return 0;
+}
+
+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 socket *sock;
+ struct sock *sk;
+ int ret;
+
+ if (tunnel->fd < 0) {
+ ret = l2tp_tunnel_sock_create(net, tunnel->tunnel_id,
+ tunnel->peer_tunnel_id, cfg,
+ &sock);
+ if (ret < 0)
+ goto err;
+ } else {
+ sock = sockfd_lookup(tunnel->fd, &ret);
+ if (!sock)
+ goto err;
+
+ ret = l2tp_validate_socket(sock->sk, net, tunnel->encap);
+ if (ret < 0)
+ goto err_sock;
+ }
+
+ sk = sock->sk;
+
+ sock_hold(sk);
+ tunnel->sock = sk;
+ tunnel->l2tp_net = net;
+
+ pn = l2tp_pernet(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);
+
+ ret = -EEXIST;
+ goto err_sock;
+ }
+ }
+ list_add_rcu(&tunnel->list, &pn->l2tp_tunnel_list);
+ spin_unlock_bh(&pn->l2tp_tunnel_list_lock);
+
+ if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
+ struct udp_tunnel_sock_cfg udp_cfg = {
+ .sk_user_data = tunnel,
+ .encap_type = UDP_ENCAP_L2TPINUDP,
+ .encap_rcv = l2tp_udp_encap_recv,
+ .encap_destroy = l2tp_udp_encap_destroy,
+ };
+
+ setup_udp_tunnel_sock(net, sock, &udp_cfg);
+ } else {
+ sk->sk_user_data = tunnel;
+ }
+
+ tunnel->old_sk_destruct = sk->sk_destruct;
+ sk->sk_destruct = &l2tp_tunnel_destruct;
+ lockdep_set_class_and_name(&sk->sk_lock.slock, &l2tp_socket_class,
+ "l2tp_sock");
+ sk->sk_allocation = GFP_ATOMIC;
+
+ if (tunnel->fd >= 0)
+ sockfd_put(sock);
+
+ return 0;
+
+err_sock:
+ if (tunnel->fd < 0)
+ sock_release(sock);
+ else
+ sockfd_put(sock);
+err:
+ return ret;
+}
+EXPORT_SYMBOL_GPL(l2tp_tunnel_register);
+
/* This function is used by the netlink TUNNEL_DELETE command.
*/
void l2tp_tunnel_delete(struct l2tp_tunnel *tunnel)
diff --git a/net/l2tp/l2tp_core.h b/net/l2tp/l2tp_core.h
index 2718d0b284d0..ba33cbec71eb 100644
--- a/net/l2tp/l2tp_core.h
+++ b/net/l2tp/l2tp_core.h
@@ -220,12 +220,14 @@ struct l2tp_session *l2tp_session_get(const struct net *net,
struct l2tp_session *l2tp_session_get_nth(struct l2tp_tunnel *tunnel, int nth);
struct l2tp_session *l2tp_session_get_by_ifname(const struct net *net,
const char *ifname);
-struct l2tp_tunnel *l2tp_tunnel_find(const struct net *net, u32 tunnel_id);
struct l2tp_tunnel *l2tp_tunnel_find_nth(const struct net *net, int nth);
int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id,
u32 peer_tunnel_id, struct l2tp_tunnel_cfg *cfg,
struct l2tp_tunnel **tunnelp);
+int l2tp_tunnel_register(struct l2tp_tunnel *tunnel, struct net *net,
+ struct l2tp_tunnel_cfg *cfg);
+
void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel);
void l2tp_tunnel_delete(struct l2tp_tunnel *tunnel);
struct l2tp_session *l2tp_session_create(int priv_size,
diff --git a/net/l2tp/l2tp_netlink.c b/net/l2tp/l2tp_netlink.c
index e7ea9c4b89ff..b05dbd9ffcb2 100644
--- a/net/l2tp/l2tp_netlink.c
+++ b/net/l2tp/l2tp_netlink.c
@@ -236,12 +236,6 @@ static int l2tp_nl_cmd_tunnel_create(struct sk_buff *skb, struct genl_info *info
if (info->attrs[L2TP_ATTR_DEBUG])
cfg.debug = nla_get_u32(info->attrs[L2TP_ATTR_DEBUG]);
- tunnel = l2tp_tunnel_find(net, tunnel_id);
- if (tunnel != NULL) {
- ret = -EEXIST;
- goto out;
- }
-
ret = -EINVAL;
switch (cfg.encap) {
case L2TP_ENCAPTYPE_UDP:
@@ -251,9 +245,19 @@ static int l2tp_nl_cmd_tunnel_create(struct sk_buff *skb, struct genl_info *info
break;
}
- if (ret >= 0)
- ret = l2tp_tunnel_notify(&l2tp_nl_family, info,
- tunnel, L2TP_CMD_TUNNEL_CREATE);
+ if (ret < 0)
+ goto out;
+
+ l2tp_tunnel_inc_refcount(tunnel);
+ ret = l2tp_tunnel_register(tunnel, net, &cfg);
+ if (ret < 0) {
+ kfree(tunnel);
+ goto out;
+ }
+ ret = l2tp_tunnel_notify(&l2tp_nl_family, info, tunnel,
+ L2TP_CMD_TUNNEL_CREATE);
+ l2tp_tunnel_dec_refcount(tunnel);
+
out:
return ret;
}
diff --git a/net/l2tp/l2tp_ppp.c b/net/l2tp/l2tp_ppp.c
index d6deca11da19..896bbca9bdaa 100644
--- a/net/l2tp/l2tp_ppp.c
+++ b/net/l2tp/l2tp_ppp.c
@@ -698,6 +698,15 @@ static int pppol2tp_connect(struct socket *sock, struct sockaddr *uservaddr,
error = l2tp_tunnel_create(sock_net(sk), fd, ver, tunnel_id, peer_tunnel_id, &tcfg, &tunnel);
if (error < 0)
goto end;
+
+ l2tp_tunnel_inc_refcount(tunnel);
+ error = l2tp_tunnel_register(tunnel, sock_net(sk),
+ &tcfg);
+ if (error < 0) {
+ kfree(tunnel);
+ goto end;
+ }
+ drop_tunnel = true;
}
} else {
/* Error if we can't find the tunnel */