[PATCH 3.18 19/56] usb: gadget: composite: fix delayed_status race condition when set_interface

[Greg Kroah-Hartman]

3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Chunfeng Yun <chunfeng.yun@xxxxxxxxxxxx>

[ Upstream commit 980900d6318066b9f8314bfb87329a20fd0d1ca4 ]

It happens when enable debug log, if set_alt() returns
USB_GADGET_DELAYED_STATUS and usb_composite_setup_continue()
is called before increasing count of @delayed_status,
so fix it by using spinlock of @cdev->lock.

Signed-off-by: Chunfeng Yun <chunfeng.yun@xxxxxxxxxxxx>
Tested-by: Jay Hsu <shih-chieh.hsu@xxxxxxxxxxxx>
Signed-off-by: Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/usb/gadget/composite.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/usb/gadget/composite.c
+++ b/drivers/usb/gadget/composite.c
@@ -1530,6 +1530,8 @@ composite_setup(struct usb_gadget *gadge
 			break;
 		if (w_value && !f->set_alt)
 			break;
+
+		spin_lock(&cdev->lock);
 		value = f->set_alt(f, w_index, w_value);
 		if (value == USB_GADGET_DELAYED_STATUS) {
 			DBG(cdev,
@@ -1539,6 +1541,7 @@ composite_setup(struct usb_gadget *gadge
 			DBG(cdev, "delayed_status count %d\n",
 					cdev->delayed_status);
 		}
+		spin_unlock(&cdev->lock);
 		break;
 	case USB_REQ_GET_INTERFACE:
 		if (ctrl->bRequestType != (USB_DIR_IN|USB_RECIP_INTERFACE))