diff options
| author | Gong, Sishuai <sishuai@purdue.edu> | 2021-04-27 15:04:24 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2021-04-27 14:23:13 -0700 |
| commit | 69e16d01d1de4f1249869de342915f608feb55d5 (patch) | |
| tree | 07ad6e46ad91358a2043adcb7e522ad71408bcd7 /net/l2tp | |
| parent | 6fd6c483e7abf0f67d02d9a49b217efcd01314f4 (diff) | |
net: fix a concurrency bug in l2tp_tunnel_register()
l2tp_tunnel_register() registers a tunnel without fully
initializing its attribute. This can allow another kernel thread
running l2tp_xmit_core() to access the uninitialized data and
then cause a kernel NULL pointer dereference error, as shown below.
Thread 1 Thread 2
//l2tp_tunnel_register()
list_add_rcu(&tunnel->list, &pn->l2tp_tunnel_list);
//pppol2tp_connect()
tunnel = l2tp_tunnel_get(sock_net(sk), info.tunnel_id);
// Fetch the new tunnel
...
//l2tp_xmit_core()
struct sock *sk = tunnel->sock;
...
bh_lock_sock(sk);
//Null pointer error happens
tunnel->sock = sk;
Fix this bug by initializing tunnel->sock before adding the
tunnel into l2tp_tunnel_list.
Reviewed-by: Cong Wang <cong.wang@bytedance.com>
Signed-off-by: Sishuai Gong <sishuai@purdue.edu>
Reported-by: Sishuai Gong <sishuai@purdue.edu>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/l2tp')
| -rw-r--r-- | net/l2tp/l2tp_core.c | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c index 2ee20743cb41..53486b162f01 100644 --- a/net/l2tp/l2tp_core.c +++ b/net/l2tp/l2tp_core.c @@ -1478,11 +1478,15 @@ int l2tp_tunnel_register(struct l2tp_tunnel *tunnel, struct net *net, tunnel->l2tp_net = net; pn = l2tp_pernet(net); + sk = sock->sk; + sock_hold(sk); + tunnel->sock = sk; + 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; } @@ -1490,10 +1494,6 @@ int l2tp_tunnel_register(struct l2tp_tunnel *tunnel, struct net *net, list_add_rcu(&tunnel->list, &pn->l2tp_tunnel_list); spin_unlock_bh(&pn->l2tp_tunnel_list_lock); - sk = sock->sk; - sock_hold(sk); - tunnel->sock = sk; - if (tunnel->encap == L2TP_ENCAPTYPE_UDP) { struct udp_tunnel_sock_cfg udp_cfg = { .sk_user_data = tunnel, |