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authorGuillaume Nault <g.nault@alphalink.fr>2018-04-10 21:01:13 +0200
committerDavid S. Miller <davem@davemloft.net>2018-04-11 17:41:27 -0400
commitf6cd651b056ffd3b4e8496afd44d4ed44bf69136 (patch)
treef616d85bc1fa0339fc227d4672cea1f4b4042a30 /net
parentl2tp: fix races in tunnel creation (diff)
downloadlinux-dev-f6cd651b056ffd3b4e8496afd44d4ed44bf69136.tar.xz
linux-dev-f6cd651b056ffd3b4e8496afd44d4ed44bf69136.zip
l2tp: fix race in duplicate tunnel detection
We can't use l2tp_tunnel_find() to prevent l2tp_nl_cmd_tunnel_create() from creating a duplicate tunnel. A tunnel can be concurrently registered after l2tp_tunnel_find() returns. Therefore, searching for duplicates must be done at registration time. Finally, remove l2tp_tunnel_find() entirely as it isn't use anywhere anymore. Fixes: 309795f4bec2 ("l2tp: Add netlink control API for L2TP") Signed-off-by: Guillaume Nault <g.nault@alphalink.fr> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/l2tp/l2tp_core.c35
-rw-r--r--net/l2tp/l2tp_core.h1
-rw-r--r--net/l2tp/l2tp_netlink.c6
3 files changed, 14 insertions, 28 deletions
diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index afb42d142807..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);
@@ -1501,6 +1481,7 @@ 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 socket *sock;
struct sock *sk;
@@ -1529,7 +1510,16 @@ int l2tp_tunnel_register(struct l2tp_tunnel *tunnel, struct net *net,
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);
@@ -1558,7 +1548,10 @@ int l2tp_tunnel_register(struct l2tp_tunnel *tunnel, struct net *net,
return 0;
err_sock:
- sockfd_put(sock);
+ if (tunnel->fd < 0)
+ sock_release(sock);
+ else
+ sockfd_put(sock);
err:
return ret;
}
diff --git a/net/l2tp/l2tp_core.h b/net/l2tp/l2tp_core.h
index 12f0fa82f162..ba33cbec71eb 100644
--- a/net/l2tp/l2tp_core.h
+++ b/net/l2tp/l2tp_core.h
@@ -220,7 +220,6 @@ 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,
diff --git a/net/l2tp/l2tp_netlink.c b/net/l2tp/l2tp_netlink.c
index 45db9b73eb1a..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: