@@ -1413,6 +1413,8 @@ static int l2cap_sock_release(struct socket *sock)
l2cap_chan_hold(chan);
l2cap_chan_lock(chan);
+ if (refcount_read(&sk->sk_refcnt) == 1)
+ chan->data = NULL;
sock_orphan(sk);
l2cap_sock_kill(sk);
@@ -1481,12 +1483,22 @@ 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;
- lock_sock(sk);
+ l2cap_chan_hold(chan);
+ l2cap_chan_lock(chan);
+ sk = chan->data;
+
+ if (!sk) {
+ l2cap_chan_unlock(chan);
+ l2cap_chan_put(chan);
+ return -ENXIO;
+ }
+ pi = l2cap_pi(sk);
+ lock_sock(sk);
if (chan->mode == L2CAP_MODE_ERTM && !list_empty(&pi->rx_busy)) {
err = -ENOMEM;
goto done;
@@ -1535,6 +1547,8 @@ static int l2cap_sock_recv_cb(struct l2cap_chan *chan, struct sk_buff *skb)
done:
release_sock(sk);
+ l2cap_chan_unlock(chan);
+ l2cap_chan_put(chan);
return err;
}
The problem occurs between the system call to close the sock and hci_rx_work, where the former releases the sock and the latter accesses it without lock protection. CPU0 CPU1 ---- ---- sock_close hci_rx_work l2cap_sock_release hci_acldata_packet l2cap_sock_kill l2cap_recv_frame sk_free l2cap_conless_channel l2cap_sock_recv_cb If hci_rx_work processes the data that needs to be received before the sock is closed, then everything is normal; Otherwise, the work thread may access the released sock when receiving data. Add a chan mutex in the rx callback of the sock to achieve synchronization between the sock release and recv cb. Reported-and-tested-by: syzbot+b7f6f8c9303466e16c8a@syzkaller.appspotmail.com Signed-off-by: Edward Adam Davis <eadavis@qq.com> --- net/bluetooth/l2cap_sock.c | 20 +++++++++++++++++--- 1 file changed, 17 insertions(+), 3 deletions(-)