usb: hub: add check for unsupported bus topology

We can't allow hubs on the 7th tier as they would allow
devices on the 8th tier.

Signed-off-by: Felipe Balbi <felipe.balbi@nokia.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

3 files changed, 8 insertions, 2 deletions

diff --git a/drivers/usb/core/devices.c b/drivers/usb/core/devices.c
index a681d9b92bda..6ec38175a817 100644
--- a/drivers/usb/core/devices.c
+++ b/drivers/usb/core/devices.c
@@ -61,8 +61,6 @@
 #include "usb.h"
 #include "hcd.h"
 
-#define MAX_TOPO_LEVEL          6
-
 /* Define ALLOW_SERIAL_NUMBER if you want to see the serial number of devices */
 #define ALLOW_SERIAL_NUMBER
 
diff --git a/drivers/usb/core/hcd.h b/drivers/usb/core/hcd.h
index 50b8bb2d1212..5b0b59b0d89b 100644
--- a/drivers/usb/core/hcd.h
+++ b/drivers/usb/core/hcd.h
@@ -21,6 +21,8 @@
 
 #include <linux/rwsem.h>
 
+#define MAX_TOPO_LEVEL          6
+
 /* This file contains declarations of usbcore internals that are mostly
  * used or exposed by Host Controller Drivers.
  */
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index e678ed8bd8c2..3251120b414e 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -1051,6 +1051,12 @@ static int hub_probe(struct usb_interface *intf, const struct usb_device_id *id)
         desc = intf->cur_altsetting;
         hdev = interface_to_usbdev(intf);
 
+        if (hdev->level == MAX_TOPO_LEVEL) {
+                dev_err(&intf->dev, "Unsupported bus topology: "
+                                "hub nested too deep\n");
+                return -E2BIG;
+        }
+
 #ifdef  CONFIG_USB_OTG_BLACKLIST_HUB
         if (hdev->parent) {
                 dev_warn(&intf->dev, "ignoring external hub\n");