char: xillybus: Check USB endpoints when probing device

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
Cc: stable <stable@kernel.org>
Closes: https://lore.kernel.org/all/0000000000001d44a6061f7a54ee@google.com/T/
Fixes: a53d120 ("char: xillybus: Add driver for XillyUSB (Xillybus variant for USB)").
Signed-off-by: Eli Billauer <eli.billauer@gmail.com>
Link: https://lore.kernel.org/r/20240816070200.50695-2-eli.billauer@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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;
 }