From:   Soenke Huster <soenke.huster@eknoes.de>
To:     Marcel Holtmann <marcel@holtmann.org>,
        Johan Hedberg <johan.hedberg@gmail.com>,
        Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>
Cc:     Soenke Huster <soenke.huster@eknoes.de>,
        linux-bluetooth@vger.kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH v2] Bluetooth: fix null ptr deref on hci_sync_conn_complete_evt
Date:   Thu, 13 Jan 2022 17:40:42 +0100
Message-Id: <20220113164042.259990-1-soenke.huster@eknoes.de>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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@eknoes.de>
---
v2: Fixed the obviously wrong boolean comparison

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 05997dff5666..d68f5640fb38 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