The patch I submitted is based on the latest kernel, 
I checked the latest kernel has the same logic, 
so I send the patch to LKML.

Thanks for your comments.


-----Original Message-----
From: Felipe Balbi [mailto:ba...@kernel.org] 
Sent: Wednesday, July 19, 2017 3:51 PM
To: He, Bo <bo...@intel.com>; linux-ker...@vger.kernel.org; 
linux-usb@vger.kernel.org
Cc: gre...@linuxfoundation.org; peter.c...@nxp.com; k.opas...@samsung.com; 
ste...@agner.ch; felixhaedi...@web.de; colin.k...@canonical.com; rog...@ti.com; 
f.faine...@gmail.com; Zhang, Yanmin <yanmin.zh...@intel.com>
Subject: RE: [PATCH] usb: gadget: udc: fix the kernel NULL pointer in 
composite_setup


Hi,

(please don't top-post and also break your lines at 80-columns ;-)

"He, Bo" <bo...@intel.com> writes:
>       1. the issue reproduced very rarely, we run reboot test
>       reproduce the issue, it reproduced two times on two board after
>       more than 1500 cycles reboot.

That's fine, we, somehow, got a use-after-free on the tracepoints. I'm 
interested in fixing that without touching udc-core since that's a dwc3-only 
bug.

>       2. the kernel version is 4.4, the test case is cold reboot, I think 
> it's not android patches cause it, it's the interrupt thread run after the 
> udc->driver->unbind.

Yeah, I need you to try v4.13-rc1. v4.4 is *really* old. I can't accept your 
patch unless I'm certain the bug still exists.

>       3. I check more drivers, like amd5536_udc_stop, at91_stop,
>       atmel_usba_stop, bcm63xx_udc_stop, s3c_hsudc_stop, all the
>       interrupt disable will be in the udc_stop(), so we need
>       guarantee to stop the interrupt then release the resource.

Right, we also disable the interrupt on ->udc_stop(). See below:

static void __dwc3_gadget_stop(struct dwc3 *dwc) {
        dwc3_gadget_disable_irq(dwc);
        __dwc3_gadget_ep_disable(dwc->eps[0]);
        __dwc3_gadget_ep_disable(dwc->eps[1]);
}

static int dwc3_gadget_stop(struct usb_gadget *g) {
        struct dwc3             *dwc = gadget_to_dwc(g);
        unsigned long           flags;
        int                     epnum;

        spin_lock_irqsave(&dwc->lock, flags);

        if (pm_runtime_suspended(dwc->dev))
                goto out;

        __dwc3_gadget_stop(dwc);

        for (epnum = 2; epnum < DWC3_ENDPOINTS_NUM; epnum++) {
                struct dwc3_ep  *dep = dwc->eps[epnum];

                if (!dep)
                        continue;

                if (!(dep->flags & DWC3_EP_END_TRANSFER_PENDING))
                        continue;

                wait_event_lock_irq(dep->wait_end_transfer,
                                    !(dep->flags & 
DWC3_EP_END_TRANSFER_PENDING),
                                    dwc->lock);
        }

out:
        dwc->gadget_driver      = NULL;
        spin_unlock_irqrestore(&dwc->lock, flags);

        free_irq(dwc->irq_gadget, dwc->ev_buf);

        return 0;
}

--
balbi
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