releases/3.16.61/usb-gadget-function-printer-avoid-wrong-list-handling-in.patch

From: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Date: Mon, 21 May 2018 20:18:07 +0900
Subject: usb: gadget: function: printer: avoid wrong list handling in
 printer_write()

commit 4a014a7339f441b0851ce012f469c0fadac61c81 upstream.

When printer_write() calls usb_ep_queue(), a udc driver (e.g.
renesas_usbhs driver) may call usb_gadget_giveback_request() in
the udc .queue ops immediately. Then, printer_write() calls
list_add(&req->list, &dev->tx_reqs_active) wrongly. After that,
if we do unbind the printer driver, WARN_ON() happens in
printer_func_unbind() because the list entry is not removed.

So, this patch moves list_add(&req->list, &dev->tx_reqs_active)
calling before usb_ep_queue().

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Acked-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.16: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 drivers/usb/gadget/printer.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/usb/gadget/printer.c
+++ b/drivers/usb/gadget/printer.c
@@ -667,19 +667,19 @@ printer_write(struct file *fd, const cha
 			return -EAGAIN;
 		}
 
+		list_add(&req->list, &dev->tx_reqs_active);
+
 		/* here, we unlock, and only unlock, to avoid deadlock. */
 		spin_unlock(&dev->lock);
 		value = usb_ep_queue(dev->in_ep, req, GFP_ATOMIC);
 		spin_lock(&dev->lock);
 		if (value) {
+			list_del(&req->list);
 			list_add(&req->list, &dev->tx_reqs);
 			spin_unlock_irqrestore(&dev->lock, flags);
 			mutex_unlock(&dev->lock_printer_io);
 			return -EAGAIN;
 		}
-
-		list_add(&req->list, &dev->tx_reqs_active);
-
 	}
 
 	spin_unlock_irqrestore(&dev->lock, flags);