[PATCH 5.10 105/112] usb: dwc3: gadget: Fix event pending check

Greg Kroah-Hartman
2022-07-19T12:27:18Z

From: Thinh Nguyen <Thinh.Nguyen@synopsys.com>

commit 7441b273388b9a59d8387a03ffbbca9d5af6348c upstream.

The DWC3_EVENT_PENDING flag is used to protect against invalid call to
top-half interrupt handler, which can occur when there's a delay in
software detection of the interrupt line deassertion.

However, the clearing of this flag was done prior to unmasking the
interrupt line, creating opportunity where the top-half handler can
come. This breaks the serialization and creates a race between the
top-half and bottom-half handler, resulting in losing synchronization
between the controller and the driver when processing events.

To fix this, make sure the clearing of the DWC3_EVENT_PENDING is done at
the end of the bottom-half handler.

Fixes: d325a1de49d6 ("usb: dwc3: gadget: Prevent losing events in event cache")
Cc: stable@vger.kernel.org
Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://lore.kernel.org/r/8670aaf1cf52e7d1e6df2a827af2d77263b93b75.1656380429.git.Thinh.Nguyen@synopsys.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/usb/dwc3/gadget.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -3781,7 +3781,6 @@ static irqreturn_t dwc3_process_event_bu
}

evt->count = 0;
- evt->flags &= ~DWC3_EVENT_PENDING;
ret = IRQ_HANDLED;

/* Unmask interrupt */
@@ -3794,6 +3793,9 @@ static irqreturn_t dwc3_process_event_bu
dwc3_writel(dwc->regs, DWC3_DEV_IMOD(0), dwc->imod_interval);
}

+ /* Keep the clearing of DWC3_EVENT_PENDING at the end */
+ evt->flags &= ~DWC3_EVENT_PENDING;
+
return ret;
}