[PATCH 2/2] char: xillybus: Check USB endpoints when probing device

[Eli Billauer <eli.billauer@gmail.com>]

Ensure, as the driver probes the device, that all endpoints that the
driver may attempt to access exist and are of the correct type.

All XillyUSB devices must have a Bulk IN and Bulk OUT endpoint at
address 1. This is verified in xillyusb_setup_base_eps().

On top of that, a XillyUSB device may have additional Bulk OUT
endpoints. The information about these endpoints' addresses is deduced
from a data structure (the IDT) that the driver fetches from the device
while probing it. These endpoints are checked in setup_channels().

A XillyUSB device never has more than one IN endpoint, as all data
towards the host is multiplexed in this single Bulk IN endpoint. This is
why setup_channels() only checks OUT endpoints.

Reported-by: syzbot+eac39cba052f2e750dbe@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/0000000000001d44a6061f7a54ee@google.com/T/
Fixes: a53d1202aef1 ("char: xillybus: Add driver for XillyUSB (Xillybus variant for USB)").
Signed-off-by: Eli Billauer <eli.billauer@gmail.com>
---
 drivers/char/xillybus/xillyusb.c | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/drivers/char/xillybus/xillyusb.c b/drivers/char/xillybus/xillyusb.c
index e12d359194f8..45771b1a3716 100644
--- a/drivers/char/xillybus/xillyusb.c
+++ b/drivers/char/xillybus/xillyusb.c
@@ -1903,6 +1903,13 @@ static const struct file_operations xillyusb_fops = {
 
 static int xillyusb_setup_base_eps(struct xillyusb_dev *xdev)
 {
+	struct usb_device *udev = xdev->udev;
+
+	/* Verify that device has the two fundamental bulk in/out endpoints */
+	if (usb_pipe_type_check(udev, usb_sndbulkpipe(udev, MSG_EP_NUM)) ||
+	    usb_pipe_type_check(udev, usb_rcvbulkpipe(udev, IN_EP_NUM)))
+		return -ENODEV;
+
 	xdev->msg_ep = endpoint_alloc(xdev, MSG_EP_NUM | USB_DIR_OUT,
 				      bulk_out_work, 1, 2);
 	if (!xdev->msg_ep)
@@ -1932,14 +1939,15 @@ static int setup_channels(struct xillyusb_dev *xdev,
 			  __le16 *chandesc,
 			  int num_channels)
 {
-	struct xillyusb_channel *chan;
+	struct usb_device *udev = xdev->udev;
+	struct xillyusb_channel *chan, *new_channels;
 	int i;
 
 	chan = kcalloc(num_channels, sizeof(*chan), GFP_KERNEL);
 	if (!chan)
 		return -ENOMEM;
 
-	xdev->channels = chan;
+	new_channels = chan;
 
 	for (i = 0; i < num_channels; i++, chan++) {
 		unsigned int in_desc = le16_to_cpu(*chandesc++);
@@ -1968,6 +1976,15 @@ static int setup_channels(struct xillyusb_dev *xdev,
 		 */
 
 		if ((out_desc & 0x80) && i < 14) { /* Entry is valid */
+			if (usb_pipe_type_check(udev,
+						usb_sndbulkpipe(udev, i + 2))) {
+				dev_err(xdev->dev,
+					"Missing BULK OUT endpoint %d\n",
+					i + 2);
+				kfree(new_channels);
+				return -ENODEV;
+			}
+
 			chan->writable = 1;
 			chan->out_synchronous = !!(out_desc & 0x40);
 			chan->out_seekable = !!(out_desc & 0x20);
@@ -1977,6 +1994,7 @@ static int setup_channels(struct xillyusb_dev *xdev,
 		}
 	}
 
+	xdev->channels = new_channels;
 	return 0;
 }
 
-- 
2.17.1