diff options
author | Gong, Sishuai <sishuai@purdue.edu> | 2021-04-27 15:04:24 +0000 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-02-06 07:52:37 +0100 |
commit | 24c7614d31c81e894623f00c51d483ea2a4db89b (patch) | |
tree | bcb247e8e995afc60d5d532b39c6715573d21862 /net/l2tp | |
parent | 1200388a0b1c3c6fda48d4d2143db8f7e4ef5348 (diff) |
net: fix a concurrency bug in l2tp_tunnel_register()
[ Upstream commit 69e16d01d1de4f1249869de342915f608feb55d5 ]
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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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 421b2c89ce12..a0ec61f2295b 100644 --- a/net/l2tp/l2tp_core.c +++ b/net/l2tp/l2tp_core.c @@ -1500,11 +1500,15 @@ 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; } @@ -1512,10 +1516,6 @@ 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, |