xhci: Fix memory leak during failed enqueue.

When the isochronous transfer support was introduced, and the xHCI driver
switched to using urb->hcpriv to store an "urb_priv" pointer, a couple of
memory leaks were introduced into the URB enqueue function in its error
handling paths.

xhci_urb_enqueue allocates urb_priv, but it doesn't free it if changing
the control endpoint's max packet size fails or the bulk endpoint is in
the middle of allocating or deallocating streams.

xhci_urb_enqueue also doesn't free urb_priv if any of the four endpoint
types' enqueue functions fail.  Instead, it expects those functions to
free urb_priv if an error occurs.  However, the bulk, control, and
interrupt enqueue functions do not free urb_priv if the endpoint ring is
NULL.  It will, however, get freed if prepare_transfer() fails in those
enqueue functions.

Several of the error paths in the isochronous endpoint enqueue function
also fail to free it.  xhci_queue_isoc_tx_prepare() doesn't free urb_priv
if prepare_ring() indicates there is not enough room for all the
isochronous TDs in this URB.  If individual isochronous TDs fail to be
queued (perhaps due to an endpoint state change), urb_priv is also leaked.

This argues that the freeing of urb_priv should be done in the function
that allocated it, xhci_urb_enqueue.

This patch looks rather ugly, but refactoring the code will have to wait
because this patch needs to be backported to stable kernels.

This patch should be backported to kernels as old as 2.6.36.
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: Andiry Xu <andiry.xu@amd.com>
Cc: stable@kernel.org

drivers/usb/host/xhci-ring.c

@@ -2500,12 +2500,9 @@ static int prepare_transfer(struct xhci_hcd *xhci,
 
 	if (td_index == 0) {
 		ret = usb_hcd_link_urb_to_ep(bus_to_hcd(urb->dev->bus), urb);
-		if (unlikely(ret)) {
-			xhci_urb_free_priv(xhci, urb_priv);
-			urb->hcpriv = NULL;
+		if (unlikely(ret))
 			return ret;
 	}
-	}
 
 	td->urb = urb;
 	/* Add this TD to the tail of the endpoint ring's TD list */

drivers/usb/host/xhci.c

@@ -1085,9 +1085,12 @@ int xhci_urb_enqueue(struct usb_hcd *hcd, struct urb *urb, gfp_t mem_flags)
 		if (urb->dev->speed == USB_SPEED_FULL) {
 			ret = xhci_check_maxpacket(xhci, slot_id,
 					ep_index, urb);
-			if (ret < 0)
+			if (ret < 0) {
+				xhci_urb_free_priv(xhci, urb_priv);
+				urb->hcpriv = NULL;
 				return ret;
 			}
+		}
 
 		/* We have a spinlock and interrupts disabled, so we must pass
 		 * atomic context to this function, which may allocate memory.
@@ -1097,6 +1100,8 @@ int xhci_urb_enqueue(struct usb_hcd *hcd, struct urb *urb, gfp_t mem_flags)
 			goto dying;
 		ret = xhci_queue_ctrl_tx(xhci, GFP_ATOMIC, urb,
 				slot_id, ep_index);
+		if (ret)
+			goto free_priv;
 		spin_unlock_irqrestore(&xhci->lock, flags);
 	} else if (usb_endpoint_xfer_bulk(&urb->ep->desc)) {
 		spin_lock_irqsave(&xhci->lock, flags);
@@ -1117,6 +1122,8 @@ int xhci_urb_enqueue(struct usb_hcd *hcd, struct urb *urb, gfp_t mem_flags)
 			ret = xhci_queue_bulk_tx(xhci, GFP_ATOMIC, urb,
 					slot_id, ep_index);
 		}
+		if (ret)
+			goto free_priv;
 		spin_unlock_irqrestore(&xhci->lock, flags);
 	} else if (usb_endpoint_xfer_int(&urb->ep->desc)) {
 		spin_lock_irqsave(&xhci->lock, flags);
@@ -1124,6 +1131,8 @@ int xhci_urb_enqueue(struct usb_hcd *hcd, struct urb *urb, gfp_t mem_flags)
 			goto dying;
 		ret = xhci_queue_intr_tx(xhci, GFP_ATOMIC, urb,
 				slot_id, ep_index);
+		if (ret)
+			goto free_priv;
 		spin_unlock_irqrestore(&xhci->lock, flags);
 	} else {
 		spin_lock_irqsave(&xhci->lock, flags);
@@ -1131,18 +1140,22 @@ int xhci_urb_enqueue(struct usb_hcd *hcd, struct urb *urb, gfp_t mem_flags)
 			goto dying;
 		ret = xhci_queue_isoc_tx_prepare(xhci, GFP_ATOMIC, urb,
 				slot_id, ep_index);
+		if (ret)
+			goto free_priv;
 		spin_unlock_irqrestore(&xhci->lock, flags);
 	}
 exit:
 	return ret;
 dying:
-	xhci_urb_free_priv(xhci, urb_priv);
-	urb->hcpriv = NULL;
 	xhci_dbg(xhci, "Ep 0x%x: URB %p submitted for "
 			"non-responsive xHCI host.\n",
 			urb->ep->desc.bEndpointAddress, urb);
+	ret = -ESHUTDOWN;
+free_priv:
+	xhci_urb_free_priv(xhci, urb_priv);
+	urb->hcpriv = NULL;
 	spin_unlock_irqrestore(&xhci->lock, flags);
-	return -ESHUTDOWN;
+	return ret;
 }
 
 /* Get the right ring for the given URB.