media: usb: siano: Fix general protection fault in smsusb

commit 31e0456 upstream.

The syzkaller USB fuzzer found a general-protection-fault bug in the
smsusb part of the Siano DVB driver.  The fault occurs during probe
because the driver assumes without checking that the device has both
IN and OUT endpoints and the IN endpoint is ep1.

By slightly rearranging the driver's initialization code, we can make
the appropriate checks early on and thus avoid the problem.  If the
expected endpoints aren't present, the new code safely returns -ENODEV
from the probe routine.

Signed-off-by: Alan Stern <[email protected]>
Reported-and-tested-by: [email protected]
CC: <[email protected]>
Reviewed-by: Johan Hovold <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Change-Id: I3eea799a4113c43448aa976f3452c0a3f7946db1

drivers/media/usb/siano/smsusb.c

@@ -351,6 +351,7 @@ static int smsusb_init_device(struct usb_interface *intf, int board_id)
 	struct smsdevice_params_t params;
 	struct smsusb_device_t *dev;
 	int i, rc;
+	int in_maxp;
 
 	/* create device object */
 	dev = kzalloc(sizeof(struct smsusb_device_t), GFP_KERNEL);
@@ -364,6 +365,24 @@ static int smsusb_init_device(struct usb_interface *intf, int board_id)
 	dev->udev = interface_to_usbdev(intf);
 	dev->state = SMSUSB_DISCONNECTED;
 
+	for (i = 0; i < intf->cur_altsetting->desc.bNumEndpoints; i++) {
+		struct usb_endpoint_descriptor *desc =
+				&intf->cur_altsetting->endpoint[i].desc;
+
+		if (desc->bEndpointAddress & USB_DIR_IN) {
+			dev->in_ep = desc->bEndpointAddress;
+			in_maxp = usb_endpoint_maxp(desc);
+		} else {
+			dev->out_ep = desc->bEndpointAddress;
+		}
+	}
+
+	sms_info("in_ep = %02x, out_ep = %02x", dev->in_ep, dev->out_ep);
+	if (!dev->in_ep || !dev->out_ep) {	/* Missing endpoints? */
+		smsusb_term_device(intf);
+		return -ENODEV;
+	}
+
 	params.device_type = sms_get_board(board_id)->type;
 
 	switch (params.device_type) {
@@ -378,24 +397,12 @@ static int smsusb_init_device(struct usb_interface *intf, int board_id)
 		/* fall-thru */
 	default:
 		dev->buffer_size = USB2_BUFFER_SIZE;
-		dev->response_alignment =
-		    le16_to_cpu(dev->udev->ep_in[1]->desc.wMaxPacketSize) -
-		    sizeof(struct sms_msg_hdr);
+		dev->response_alignment = in_maxp - sizeof(struct sms_msg_hdr);
 
 		params.flags |= SMS_DEVICE_FAMILY2;
 		break;
 	}
 
-	for (i = 0; i < intf->cur_altsetting->desc.bNumEndpoints; i++) {
-		if (intf->cur_altsetting->endpoint[i].desc. bEndpointAddress & USB_DIR_IN)
-			dev->in_ep = intf->cur_altsetting->endpoint[i].desc.bEndpointAddress;
-		else
-			dev->out_ep = intf->cur_altsetting->endpoint[i].desc.bEndpointAddress;
-	}
-
-	sms_info("in_ep = %02x, out_ep = %02x",
-		dev->in_ep, dev->out_ep);
-
 	params.device = &dev->udev->dev;
 	params.buffer_size = dev->buffer_size;
 	params.num_buffers = MAX_BUFFERS;