linux-kernel - [PATCH] Bluetooth: fix division by zero in send path

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Message-Id: <20211025113944.4350-1-johan@kernel.org>
Date:   Mon, 25 Oct 2021 13:39:44 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Marcel Holtmann <marcel@...tmann.org>
Cc:     Johan Hedberg <johan.hedberg@...il.com>,
        Luiz Augusto von Dentz <luiz.dentz@...il.com>,
        linux-bluetooth@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, Johan Hovold <johan@...nel.org>,
        stable@...r.kernel.org
Subject: [PATCH] Bluetooth: fix division by zero in send path

Add the missing bulk-out endpoint sanity check to probe() to avoid
division by zero in bfusb_send_frame() in case a malicious device has
broken descriptors (or when doing descriptor fuzz testing).

Note that USB core will reject URBs submitted for endpoints with zero
wMaxPacketSize but that drivers doing packet-size calculations still
need to handle this (cf. commit 2548288b4fb0 ("USB: Fix: Don't skip
endpoint descriptors with maxpacket=0")).

Cc: stable@...r.kernel.org
Signed-off-by: Johan Hovold <johan@...nel.org>
---
 drivers/bluetooth/bfusb.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/bluetooth/bfusb.c b/drivers/bluetooth/bfusb.c
index 5a321b4076aa..df80fb324356 100644
--- a/drivers/bluetooth/bfusb.c
+++ b/drivers/bluetooth/bfusb.c
@@ -627,6 +627,8 @@ static int bfusb_probe(struct usb_interface *intf, const struct usb_device_id *i
 	data->bulk_in_ep    = bulk_in_ep->desc.bEndpointAddress;
 	data->bulk_out_ep   = bulk_out_ep->desc.bEndpointAddress;
 	data->bulk_pkt_size = le16_to_cpu(bulk_out_ep->desc.wMaxPacketSize);
+	if (!data->bulk_pkt_size)
+		goto done;
 
 	rwlock_init(&data->lock);
 
-- 
2.32.0