usb: rh_call_control tbuf overflow fix

rh_call_control() contains a buffer, tbuf, which it uses to hold
USB descriptors. These discriptors are eventually copied into the
transfer_buffer in the URB. The buffer in the URB is dynamically
defined and is always large enough to hold the amount of data it
requests.

tbuf is currently statically allocated on the stack with a size
of 15 bytes, regardless of the size specified in the URB.
This patch dynamically allocates tbuf, and ensures that tbuf is
at least as big as the buffer in the URB.

If an hcd attempts to write a descriptor containing more than
15 bytes ( such as the Standard BOS Descriptor for hubs, defined
in the USB3.0 Spec, section 10.13.1 ) the write would overflow
the buffer and corrupt the stack. This patch addresses this
behavior.

Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Sean O. Stalley <sean.stalley@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/core/hcd.c

@@ -466,17 +466,13 @@ static int rh_call_control (struct usb_hcd *hcd, struct urb *urb)
 	struct usb_ctrlrequest *cmd;
  	u16		typeReq, wValue, wIndex, wLength;
 	u8		*ubuf = urb->transfer_buffer;
-	/*
-	 * tbuf should be as big as the BOS descriptor and
-	 * the USB hub descriptor.
-	 */
-	u8		tbuf[USB_DT_BOS_SIZE + USB_DT_USB_SS_CAP_SIZE]
-		__attribute__((aligned(4)));
-	const u8	*bufp = tbuf;
 	unsigned	len = 0;
 	int		status;
 	u8		patch_wakeup = 0;
 	u8		patch_protocol = 0;
+	u16		tbuf_size;
+	u8		*tbuf = NULL;
+	const u8	*bufp;
 
 	might_sleep();
 
@@ -496,6 +492,18 @@ static int rh_call_control (struct usb_hcd *hcd, struct urb *urb)
 	if (wLength > urb->transfer_buffer_length)
 		goto error;
 
+	/*
+	 * tbuf should be at least as big as the
+	 * USB hub descriptor.
+	 */
+	tbuf_size =  max_t(u16, sizeof(struct usb_hub_descriptor), wLength);
+	tbuf = kzalloc(tbuf_size, GFP_KERNEL);
+	if (!tbuf)
+		return -ENOMEM;
+
+	bufp = tbuf;
+
+
 	urb->actual_length = 0;
 	switch (typeReq) {
 
@@ -693,6 +701,8 @@ error:
 				bDeviceProtocol = USB_HUB_PR_HS_SINGLE_TT;
 	}
 
+	kfree(tbuf);
+
 	/* any errors get returned through the urb completion */
 	spin_lock_irq(&hcd_root_hub_lock);
 	usb_hcd_unlink_urb_from_ep(hcd, urb);