Subject: [PATCH AUTOSEL 5.10 062/176] Bluetooth: skip invalid hci_sync_conn_complete_evt

From: Sasha Levin <[email-masked]>
Date: Thu, 9 Sep 2021 07:49:24 -0400

From: Desmond Cheong Zhi Xi <[email-masked]>

[ Upstream commit 92fe24a7db751b80925214ede43f8d2be792ea7b ]

Syzbot reported a corrupted list in kobject_add_internal [1]. This
happens when multiple HCI_EV_SYNC_CONN_COMPLETE event packets with
status 0 are sent for the same HCI connection. This causes us to
register the device more than once which corrupts the kset list.

As this is forbidden behavior, we add a check for whether we're
trying to process the same HCI_EV_SYNC_CONN_COMPLETE event multiple
times for one connection. If that's the case, the event is invalid, so
we report an error that the device is misbehaving, and ignore the
packet.

Link: https://syzkaller.appspot.com/bug?extid=66264bf2fd0476be7e6c [1]
Reported-by: [email-masked]
Tested-by: [email-masked]
Signed-off-by: Desmond Cheong Zhi Xi <[email-masked]>
Signed-off-by: Marcel Holtmann <[email-masked]>
Signed-off-by: Sasha Levin <[email-masked]>
---
 net/bluetooth/hci_event.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index e59ae24a8f17..45de2d8b9a9d 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -4329,6 +4329,21 @@ static void hci_sync_conn_complete_evt(struct hci_dev *hdev,
 
 	switch (ev->status) {
 	case 0x00:
+		/* The synchronous connection complete event should only be
+		 * sent once per new connection. Receiving a successful
+		 * complete event when the connection status is already
+		 * BT_CONNECTED means that the device is misbehaving and sent
+		 * multiple complete event packets for the same new connection.
+		 *
+		 * Registering the device more than once can corrupt kernel
+		 * memory, hence upon detecting this invalid event, we report
+		 * an error and ignore the packet.
+		 */
+		if (conn->state == BT_CONNECTED) {
+			bt_dev_err(hdev, "Ignoring connect complete event for existing connection");
+			goto unlock;
+		}
+
 		conn->handle = __le16_to_cpu(ev->handle);
 		conn->state  = BT_CONNECTED;
 		conn->type   = ev->link_type;
-- 
2.30.2