[v2] usb: gadget: function: printer: avoid wrong list handling in printer_write()

Commit Message

Yoshihiro Shimoda May 21, 2018, 11:18 a.m. UTC

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 <[e-mail]>
Acked-by: Felipe Balbi <[e-mail]>
---
 Changes from RFC (v1):
  - Modify the implementation to fix the issue.
  - Add "Acked-by Felipe Balbi".
  - Remove RFC.
  - Revise commit log.

 drivers/usb/gadget/function/f_printer.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

Comments

Felipe Balbi May 21, 2018, 12:24 p.m. UTC | #1

Hi Greg,

Yoshihiro Shimoda <[e-mail]> writes:
> 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 <[e-mail]>
> Acked-by: Felipe Balbi <[e-mail]>

I'm not sure if you're still taking bug fixes for current -rc cycle, but
if you are, please take this directly. If you're done with v4.17, please
apply this on top of my pull request which I sent an hour or so ago.

Thanks

Patch

diff --git a/drivers/usb/gadget/function/f_printer.c b/drivers/usb/gadget/function/f_printer.c
index d359efe..9c7ed25 100644
--- a/drivers/usb/gadget/function/f_printer.c
+++ b/drivers/usb/gadget/function/f_printer.c
@@ -631,19 +631,19 @@  static void tx_complete(struct usb_ep *ep, struct usb_request *req)
 			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);