usb: gadgetfs: restrict upper bound on device configuration size

Andrey Konovalov reported that we were not properly checking the upper
limit before of a device configuration size before calling
memdup_user(), which could cause some problems.

So set the upper limit to PAGE_SIZE * 4, which should be good enough for
all devices.

Reported-by: Andrey Konovalov <andreyknvl@google.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

diff --git a/drivers/usb/gadget/legacy/inode.c b/drivers/usb/gadget/legacy/inode.c
index e8f4102d19df54fa1983578f8f773067ee317d92..48f1409b438adeec1eb066a66bf6ab4c894d65cc 100644 (file)
--- a/drivers/usb/gadget/legacy/inode.c
+++ b/drivers/usb/gadget/legacy/inode.c
@@ -1762,7 +1762,8 @@ dev_config (struct file *fd, const char __user *buf, size_t len, loff_t *ptr)
        }
        spin_unlock_irq(&dev->lock);
 
-       if (len < (USB_DT_CONFIG_SIZE + USB_DT_DEVICE_SIZE + 4))
+       if ((len < (USB_DT_CONFIG_SIZE + USB_DT_DEVICE_SIZE + 4)) ||
+           (len > PAGE_SIZE * 4))
                return -EINVAL;
 
        /* we might need to change message format someday */