linux-kernel - [PATCH v2 1/2] Bluetooth: hci_sync: Avoid use-after-free in dbg for hci_remove_adv

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Message-ID: <20230630150906.v2.1.I3b7c8905728f3124576361ca35ed28e37f12f5d1@changeid>
Date:   Fri, 30 Jun 2023 15:09:06 -0700
From:   Douglas Anderson <dianders@...omium.org>
To:     Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        Luiz Augusto von Dentz <luiz.dentz@...il.com>
Cc:     Stephen Boyd <swboyd@...omium.org>,
        Douglas Anderson <dianders@...omium.org>,
        Manish Mandlik <mmandlik@...gle.com>,
        Miao-chen Chou <mcchou@...gle.com>,
        linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 1/2] Bluetooth: hci_sync: Avoid use-after-free in dbg for hci_remove_adv_monitor()

KASAN reports that there's a use-after-free in
hci_remove_adv_monitor(). Trawling through the disassembly, you can
see that the complaint is from the access in bt_dev_dbg() under the
HCI_ADV_MONITOR_EXT_MSFT case. The problem case happens because
msft_remove_monitor() can end up freeing the monitor
structure. Specifically:
  hci_remove_adv_monitor() ->
  msft_remove_monitor() ->
  msft_remove_monitor_sync() ->
  msft_le_cancel_monitor_advertisement_cb() ->
  hci_free_adv_monitor()

Moving the printout to before the memory is freed.

Fixes: 7cf5c2978f23 ("Bluetooth: hci_sync: Refactor remove Adv Monitor")
Signed-off-by: Douglas Anderson <dianders@...omium.org>
---

Changes in v2:
- Move the print, don't stash handle in a local.

 net/bluetooth/hci_core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index 48917c68358d..7e2ecf8a55d8 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -1980,9 +1980,9 @@ static int hci_remove_adv_monitor(struct hci_dev *hdev,
 		goto free_monitor;
 
 	case HCI_ADV_MONITOR_EXT_MSFT:
-		status = msft_remove_monitor(hdev, monitor);
 		bt_dev_dbg(hdev, "%s remove monitor %d msft status %d",
 			   hdev->name, monitor->handle, status);
+		status = msft_remove_monitor(hdev, monitor);
 		break;
 	}
 
-- 
2.41.0.255.g8b1d071c50-goog