Re: [syzbot] [bluetooth?] general protection fault in l2cap_sock_recv_cb
From: Edward Adam Davis
Date: Fri Jun 21 2024 - 11:02:26 EST
please test null ptr defref in l2cap_sock_recv_cb
#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git cc8ed4d0a848
diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c
index 6db60946c627..c0fe74a6b45e 100644
--- a/net/bluetooth/l2cap_sock.c
+++ b/net/bluetooth/l2cap_sock.c
@@ -47,6 +47,7 @@ static void l2cap_sock_init(struct sock *sk, struct sock *parent);
static struct sock *l2cap_sock_alloc(struct net *net, struct socket *sock,
int proto, gfp_t prio, int kern);
static void l2cap_sock_cleanup_listen(struct sock *parent);
+static DEFINE_MUTEX(chan_data_lock);
bool l2cap_is_socket(struct socket *sock)
{
@@ -1239,6 +1240,9 @@ static void l2cap_sock_kill(struct sock *sk)
BT_DBG("sk %p state %s", sk, state_to_string(sk->sk_state));
+ mutex_lock(&chan_data_lock);
+ l2cap_pi(sk)->chan->data = NULL;
+ mutex_unlock(&chan_data_lock);
/* Kill poor orphan */
l2cap_chan_put(l2cap_pi(sk)->chan);
@@ -1481,10 +1485,18 @@ static struct l2cap_chan *l2cap_sock_new_connection_cb(struct l2cap_chan *chan)
static int l2cap_sock_recv_cb(struct l2cap_chan *chan, struct sk_buff *skb)
{
- struct sock *sk = chan->data;
- struct l2cap_pinfo *pi = l2cap_pi(sk);
+ struct sock *sk;
+ struct l2cap_pinfo *pi;
int err;
+ mutex_lock(&chan_data_lock);
+ sk = chan->data;
+ if (!sk) {
+ mutex_unlock(&chan_data_lock);
+ return -ENXIO;
+ }
+
+ pi = l2cap_pi(sk);
lock_sock(sk);
if (chan->mode == L2CAP_MODE_ERTM && !list_empty(&pi->rx_busy)) {
@@ -1535,6 +1547,7 @@ static int l2cap_sock_recv_cb(struct l2cap_chan *chan, struct sk_buff *skb)
done:
release_sock(sk);
+ mutex_unlock(&chan_data_lock);
return err;
}