Commit 11eb85ec authored Jan 15, 2020 by Dan Carpenter Committed by Johan Hedberg Jan 26, 2020

Bluetooth: Fix race condition in hci_release_sock()



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>

parent 18f81241

net/bluetooth/hci_sock.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -839,6 +839,8 @@ 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);
		@@ -886,6 +888,7 @@ 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;
		}

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