usb: gadget: function: printer: avoid wrong list handling in printer_write()

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>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/gadget/function/f_printer.c b/drivers/usb/gadget/function/f_printer.c
index d359efe06c769d9f63235c4b562dbe2f97d97e04..9c7ed2539ff7727c64427d76a681a063c82937b7 100644 (file)
--- a/drivers/usb/gadget/function/f_printer.c
+++ b/drivers/usb/gadget/function/f_printer.c
@@ -631,19 +631,19 @@ printer_write(struct file *fd, const char __user *buf, size_t len, loff_t *ptr)
                        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);