[PATCH] usbip: vudc: fix NULL pointer dereference in vep_dequeue

[Jipa Alexandru-Ionut <jipaionut@gmail.com>]

vep_dequeue() reads the udc from req->udc, but struct vrequest's udc
field is never assigned anywhere in the driver, so it is always NULL.
The following dereference of udc->driver then oopses.

vep_queue(), the symmetric path, correctly derives the udc from the
endpoint via ep_to_vudc(ep); vep_dequeue() must do the same.

This is only reached when a request is queued at the time of dequeue.
A FunctionFS gadget keeps OUT requests queued, so unbinding such a
gadget from a usbip-vudc UDC (ffs_func_unbind -> usb_ep_dequeue)
hits it and wedges the vudc subsystem.

Fixes: b6a0ca111867 ("usbip: vudc: Add UDC specific ops")
Cc: stable@vger.kernel.org
Signed-off-by: Jipa Alexandru-Ionut <jipaionut@gmail.com>
---
 drivers/usb/usbip/vudc_dev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/usbip/vudc_dev.c b/drivers/usb/usbip/vudc_dev.c
index 100000000000..100000000001 100644
--- a/drivers/usb/usbip/vudc_dev.c
+++ b/drivers/usb/usbip/vudc_dev.c
@@ -344,7 +344,7 @@ static int vep_dequeue(struct usb_ep *_ep, struct usb_request *_req)

 	ep = to_vep(_ep);
 	req = to_vrequest(_req);
-	udc = req->udc;
+	udc = ep_to_vudc(ep);

 	if (!udc->driver)
 		return -ESHUTDOWN;
--
2.47.0