[PATCH 3.16 086/366] usb: gadget: function: printer: avoid wrong list handling in printer_write()

Ben Hutchings
2018-11-11T20:18:10Z

From: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>

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);