netdev - [PATCH] Bluetooth: fix null ptr deref on hci_sync_conn_complete

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Date:   Thu, 13 Jan 2022 10:05:52 +0100
From:   Soenke Huster <soenke.huster@...oes.de>
To:     me@...oes.de, Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        Luiz Augusto von Dentz <luiz.dentz@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Soenke Huster <soenke.huster@...oes.de>,
        linux-bluetooth@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] Bluetooth: fix null ptr deref on hci_sync_conn_complete_evt

This event is specified just for SCO and eSCO link types.
On the reception of a HCI_Synchronous_Connection_Complete for a BDADDR
of an existing LE connection, LE link type and a status that triggers the
second case of the packet processing a NULL pointer dereference happens,
as conn->link is NULL.

Signed-off-by: Soenke Huster <soenke.huster@...oes.de>
---
I found this null pointer dereference while fuzzing bluetooth-next. 
On the described behaviour, a null ptr deref in line 4723 happens, as 
conn->link is NULL. According to the Core spec, Link_Type must be SCO or eSCO,
all other values are reserved for future use. Checking that mitigates a null 
pointer dereference.

 net/bluetooth/hci_event.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index fc30f4c03d29..fc3f29d195d2 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -4661,6 +4661,11 @@ static void hci_sync_conn_complete_evt(struct hci_dev *hdev, void *data,
 	struct hci_ev_sync_conn_complete *ev = data;
 	struct hci_conn *conn;
 
+	if (ev->link_type != SCO_LINK || ev->link_type != ESCO_LINK) {
+		bt_dev_err(hdev, "Ignoring connect complete event for invalid link type");
+		return;
+	}
+
 	bt_dev_dbg(hdev, "status 0x%2.2x", ev->status);
 
 	hci_dev_lock(hdev);
-- 
2.34.1