Bluetooth: Fix race condition in hci_release_sock()

commit 11eb85ec42dc8c7a7ec519b90ccf2eeae9409de8 upstream.

Syzbot managed to trigger a use after free "KASAN: use-after-free Write
in hci_sock_bind".  I have reviewed the code manually and one possibly
cause I have found is that we are not holding lock_sock(sk) when we do
the hci_dev_put(hdev) in hci_sock_release().  My theory is that the bind
and the release are racing against each other which results in this use
after free.

Reported-by: syzbot+eba992608adf3d796bcc@syzkaller.appspotmail.com
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/bluetooth/hci_sock.c b/net/bluetooth/hci_sock.c
index d4e2a16..e506c51 100644 (file)
--- a/net/bluetooth/hci_sock.c
+++ b/net/bluetooth/hci_sock.c
@@ -831,6 +831,8 @@ static int hci_sock_release(struct socket *sock)
        if (!sk)
                return 0;
 
+       lock_sock(sk);
+
        switch (hci_pi(sk)->channel) {
        case HCI_CHANNEL_MONITOR:
                atomic_dec(&monitor_promisc);
@@ -878,6 +880,7 @@ static int hci_sock_release(struct socket *sock)
        skb_queue_purge(&sk->sk_receive_queue);
        skb_queue_purge(&sk->sk_write_queue);
 
+       release_sock(sk);
        sock_put(sk);
        return 0;
 }