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Subject[PATCH 2/2] usb: mtu3: fix race condition about delayed_status
Date
usb_composite_setup_continue() may be called before composite_setup()
return USB_GADGET_DELAYED_STATUS, then the controller driver will
delay status stage after composite_setup() finish, but the class driver
don't ask the controller to continue delayed status anymore, this will
cause control transfer timeout.

happens when use mass storage (also enabled other class driver):

cpu1: cpu2
handle_setup(SET_CONFIG) //gadget driver
unlock (g->lock)
gadget_driver->setup()
composite_setup()
lock(cdev->lock)
set_config()
fsg_set_alt() // maybe some times due to many class are enabled
raise FSG_STATE_CONFIG_CHANGE
return USB_GADGET_DELAYED_STATUS
handle_exception()
usb_composite_setup_continue()
unlock(cdev->lock)
lock(cdev->lock)
ep0_queue()
lock (g->lock)
//no delayed status, nothing todo
unlock (g->lock)
unlock(cdev->lock)
return USB_GADGET_DELAYED_STATUS // composite_setup
lock (g->lock)
get USB_GADGET_DELAYED_STATUS //handle_setup [1]

Try to fix the race condition as following:
After the driver gets USB_GADGET_DELAYED_STATUS at [1], if we find
there is a usb_request in ep0 request list, it means composite already
asked us to continue delayed status by usb_composite_setup_continue(),
so we skip request about delayed_status by composite_setup() and still
do status stage.

Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
---
drivers/usb/mtu3/mtu3_gadget_ep0.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/mtu3/mtu3_gadget_ep0.c b/drivers/usb/mtu3/mtu3_gadget_ep0.c
index df3fd055792f..2be182bd793a 100644
--- a/drivers/usb/mtu3/mtu3_gadget_ep0.c
+++ b/drivers/usb/mtu3/mtu3_gadget_ep0.c
@@ -671,8 +671,16 @@ __acquires(mtu->lock)
if (mtu->test_mode) {
; /* nothing to do */
} else if (handled == USB_GADGET_DELAYED_STATUS) {
- /* handle the delay STATUS phase till receive ep_queue on ep0 */
- mtu->delayed_status = true;
+
+ mreq = next_ep0_request(mtu);
+ if (mreq) {
+ /* already asked us to continue delayed status */
+ ep0_do_status_stage(mtu);
+ ep0_req_giveback(mtu, &mreq->request);
+ } else {
+ /* do delayed STATUS stage till receive ep0_queue */
+ mtu->delayed_status = true;
+ }
} else if (le16_to_cpu(setup.wLength) == 0) { /* no data stage */

ep0_do_status_stage(mtu);
--
2.23.0
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