| Message ID | 20200115174903.shuanlfvnly3anqk@kili.mountain |
|---|---|
| State | Awaiting Upstream |
| Delegated to: | David Miller |
| Headers | show |
| Series | Bluetooth: Fix race condition in hci_release_sock() | expand |
Hi Dan, On Wed, Jan 15, 2020, Dan Carpenter wrote: > 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> > --- > Not tested! Please review very very carefully! > > I feel like maybe someone should audit the (struct proto_ops)->release() > functions because there may be similar bugs to this in other drivers. > > net/bluetooth/hci_sock.c | 3 +++ > 1 file changed, 3 insertions(+) The patch looks correct to me since it's following the same locking conventions as all the other socket callbacks in hci_sock.c. I also verified that it doesn't cause regressions in the various socket testers we have in user space BlueZ (e.g. tools/l2cap-tester). The patch is now applied to the bluetooth-next tree. Thanks! Johan
diff --git a/net/bluetooth/hci_sock.c b/net/bluetooth/hci_sock.c index 5d0ed28c0d3a..c86598ff4283 100644 --- 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; }
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> --- Not tested! Please review very very carefully! I feel like maybe someone should audit the (struct proto_ops)->release() functions because there may be similar bugs to this in other drivers. net/bluetooth/hci_sock.c | 3 +++ 1 file changed, 3 insertions(+)