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From:   Peter Chen <peter.chen@nxp.com>
To:     Marek Szyprowski <m.szyprowski@samsung.com>
CC:     "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Felipe Balbi <balbi@kernel.org>,
        Minas Harutyunyan <hminas@synopsys.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [PATCH] usb: gadget: udc: Flush pending work also in error path
Thread-Topic: [PATCH] usb: gadget: udc: Flush pending work also in error path
Thread-Index: AQHWW2gRyaXWYCsNREqGl03uUDVrwakLJniA
Date:   Fri, 17 Jul 2020 03:59:20 +0000
Message-ID: <20200717035917.GB17070@b29397-desktop>
References: <CGME20200716115546eucas1p1deb159dd37bc1211f4579d4d85f9af92@eucas1p1.samsung.com>
 <20200716115525.27519-1-m.szyprowski@samsung.com>
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On 20-07-16 13:55:25, Marek Szyprowski wrote:
> When binding an UDC driver to the pending gadget fails in
> check_pending_gadget_drivers(), the usb_add_gadget_udc_release() function
> ends without waiting for the usb_gadget_state_work to finish, what in
> turn might cause the whole struct usb_gadget being freed by the caller
> before the usb_gadget_state_work being executed.
>=20
> This can be observed on some boards with USB Mass Storage gadget
> compiled-in and kernel booted without the needed module parameters:
>=20
> dwc2 12480000.hsotg: dwc2_check_params: Invalid parameter besl=3D1
> dwc2 12480000.hsotg: dwc2_check_params: Invalid parameter g_np_tx_fifo_si=
ze=3D1024
> dwc2 12480000.hsotg: EPs: 16, dedicated fifos, 7808 entries in SPRAM
> Mass Storage Function, version: 2009/09/11
> LUN: removable file: (no medium)
> no file given for LUN0
> g_mass_storage 12480000.hsotg: failed to start g_mass_storage: -22
> dwc2: probe of 12480000.hsotg failed with error -22
> 8<--- cut here ---
> Unable to handle kernel NULL pointer dereference at virtual address 00000=
004
> pgd =3D (ptrval)
> [00000004] *pgd=3D00000000
> Internal error: Oops: 5 [#1] PREEMPT SMP ARM
> Modules linked in:
> CPU: 1 PID: 88 Comm: kworker/1:2 Not tainted 5.8.0-rc5-next-20200715-0006=
2-gc5bb489ae825-dirty #8792
> Hardware name: Samsung Exynos (Flattened Device Tree)
> Workqueue:  0x0 (rcu_gp)
> PC is at process_one_work+0x44/0x7dc
> ...
> Process kworker/1:2 (pid: 88, stack limit =3D 0x(ptrval))
> Stack: (0xed9f1f00 to 0xed9f2000)
> ...
> [<c0148590>] (process_one_work) from [<c0148d6c>] (worker_thread+0x44/0x5=
1c)
> [<c0148d6c>] (worker_thread) from [<c01500c0>] (kthread+0x158/0x1a0)
> [<c01500c0>] (kthread) from [<c0100114>] (ret_from_fork+0x14/0x20)
> Exception stack(0xed9f1fb0 to 0xed9f1ff8)
> ...
> ---[ end trace 5033c1326a62e5f3 ]---
> note: kworker/1:2[88] exited with preempt_count 1
>=20
> Fix this by flushing pending work in error path.
>=20
> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
> ---
>  drivers/usb/gadget/udc/core.c | 1 +
>  1 file changed, 1 insertion(+)
>=20
> diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.=
c
> index c33ad8a333ad..4f82bcd31fd3 100644
> --- a/drivers/usb/gadget/udc/core.c
> +++ b/drivers/usb/gadget/udc/core.c
> @@ -1230,6 +1230,7 @@ int usb_add_gadget_udc_release(struct device *paren=
t, struct usb_gadget *gadget,
>  	return 0;
> =20
>   err_del_udc:
> +	flush_work(&gadget->work);
>  	device_del(&udc->dev);
> =20
>   err_unlist_udc:
> --=20
> 2.17.1
>=20

Reviewed-by: Peter Chen <peter.chen@nxp.com>

--=20

Thanks,
Peter Chen=