[PATCH] usb: gadget: forbid queuing request to a disabled ep

[changbin.du@intel.com]

From: "Du, Changbin" <changbin.du@intel.com>

Queue a request to disabled ep  doesn't make sense, and induce caller
make mistakes.

Here is a example for the android mtp gadget function driver. A mem
corruption can happen on below senario.
1) On disconnect, mtp driver disable its EPs,
2) During send_file_work and receive_file_work, mtp queues a request
   to ep. (The mtp driver need improve its synchronization logic!)
3) mtp_function_unbind is invoked and all mtp requests are freed.
4) when udc process the request queued on step 2, will cause kernel
   NULL pointer dereference exception.

Signed-off-by: Du, Changbin <changbin.du@intel.com>
---
This patch is seprated from below patches because gadget layer has
added the 'enabled' flag in v4.4. so abandon it and submit new one.
[PATCH 0/2] Two fix for dwc2 gadget driver
  usb: dwc2: add ep enabled flag to avoid double enable/disable
  usb: dwc2: forbid queuing request to a disabled ep

---
 include/linux/usb/gadget.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
index 3d583a1..d813bd2 100644
--- a/include/linux/usb/gadget.h
+++ b/include/linux/usb/gadget.h
@@ -402,6 +402,9 @@ static inline void usb_ep_free_request(struct usb_ep *ep,
 static inline int usb_ep_queue(struct usb_ep *ep,
 			       struct usb_request *req, gfp_t gfp_flags)
 {
+	if (!ep->enabled)
+		return -ESHUTDOWN;
+
 	return ep->ops->queue(ep, req, gfp_flags);
 }
 
-- 
2.5.0