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Date:   Fri, 17 Jul 2020 03:59:20 +0000
From:   Peter Chen <peter.chen@....com>
To:     Marek Szyprowski <m.szyprowski@...sung.com>
CC:     "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Felipe Balbi <balbi@...nel.org>,
        Minas Harutyunyan <hminas@...opsys.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] usb: gadget: udc: Flush pending work also in error path

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.
> 
> This can be observed on some boards with USB Mass Storage gadget
> compiled-in and kernel booted without the needed module parameters:
> 
> dwc2 12480000.hsotg: dwc2_check_params: Invalid parameter besl=1
> dwc2 12480000.hsotg: dwc2_check_params: Invalid parameter g_np_tx_fifo_size=1024
> 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 00000004
> pgd = (ptrval)
> [00000004] *pgd=00000000
> 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-20200715-00062-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 = 0x(ptrval))
> Stack: (0xed9f1f00 to 0xed9f2000)
> ...
> [<c0148590>] (process_one_work) from [<c0148d6c>] (worker_thread+0x44/0x51c)
> [<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
> 
> Fix this by flushing pending work in error path.
> 
> Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
> ---
>  drivers/usb/gadget/udc/core.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> 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 *parent, struct usb_gadget *gadget,
>  	return 0;
>  
>   err_del_udc:
> +	flush_work(&gadget->work);
>  	device_del(&udc->dev);
>  
>   err_unlist_udc:
> -- 
> 2.17.1
> 

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

-- 

Thanks,
Peter Chen

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