[PATCH] Bluetooth: do not send mgmt commands to device which is going to close

[Dmitry Antipov <dmantipov@xxxxxxxxx>]

Syzbot has observed the following race between 'hci_dev_close()' and
'hci_cmd_sync_work()':

T0:                             T1:

...
-> sock_ioctl()
 -> sock_do_ioctl()
  -> hci_dev_close()
   -> hci_dev_close_sync()
    -> __mgmt_power_off()        ...
     -> mgmt_pending_foreach()   -> process_scheduled_works()
      -> settings_rsp()           -> hci_cmd_sync_work()
       -> kfree()                  -> set_powered_sync()

That is, 'hci_cmd_sync_work()' makes an attempt to process a command
from (partially) freed 'cmd_sync_work_list', which causes UAF detected
by KASAN. Fix this by marking the closing device with HCI_CLOSING bit
very early and rejecting new mgmt commands for such a device.

Reported-by: syzbot+03d6270b6425df1605bf@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=03d6270b6425df1605bf
Signed-off-by: Dmitry Antipov <dmantipov@xxxxxxxxx>
---
 include/net/bluetooth/hci.h | 1 +
 net/bluetooth/hci_core.c    | 4 ++++
 net/bluetooth/hci_sock.c    | 5 +++++
 3 files changed, 10 insertions(+)

diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
index bab1e3d7452a..492723a22e68 100644
--- a/include/net/bluetooth/hci.h
+++ b/include/net/bluetooth/hci.h
@@ -345,6 +345,7 @@ enum {
 	HCI_UP,
 	HCI_INIT,
 	HCI_RUNNING,
+	HCI_CLOSING,
 
 	HCI_PSCAN,
 	HCI_ISCAN,
diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index 629c302f7407..95f55cfb6da6 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -501,12 +501,16 @@ int hci_dev_close(__u16 dev)
 		goto done;
 	}
 
+	set_bit(HCI_CLOSING, &hdev->flags);
+
 	cancel_work_sync(&hdev->power_on);
 	if (hci_dev_test_and_clear_flag(hdev, HCI_AUTO_OFF))
 		cancel_delayed_work(&hdev->power_off);
 
 	err = hci_dev_do_close(hdev);
 
+	if (unlikely(err))
+		clear_bit(HCI_CLOSING, &hdev->flags);
 done:
 	hci_dev_put(hdev);
 	return err;
diff --git a/net/bluetooth/hci_sock.c b/net/bluetooth/hci_sock.c
index 2272e1849ebd..ff43718822d4 100644
--- a/net/bluetooth/hci_sock.c
+++ b/net/bluetooth/hci_sock.c
@@ -1671,6 +1671,11 @@ static int hci_mgmt_cmd(struct hci_mgmt_chan *chan, struct sock *sk,
 			goto done;
 		}
 
+		if (unlikely(test_bit(HCI_CLOSING, &hdev->flags))) {
+			err = -ENODEV;
+			goto done;
+		}
+
 		if (hci_dev_test_flag(hdev, HCI_SETUP) ||
 		    hci_dev_test_flag(hdev, HCI_CONFIG) ||
 		    hci_dev_test_flag(hdev, HCI_USER_CHANNEL)) {
-- 
2.46.2