linux-kernel - Re: [PATCH] usb: cdnsp: Fix lack of spin_lock_irqsave/spin_lock

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Date:   Mon, 13 Dec 2021 21:29:46 +0800
From:   Peter Chen <peter.chen@...nel.org>
To:     Pawel Laszczak <pawell@...ence.com>
Cc:     gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, jianhe@...arella.com,
        stable@...r.kernel.org
Subject: Re: [PATCH] usb: cdnsp: Fix lack of
 spin_lock_irqsave/spin_lock_restore

On 21-12-13 13:20:01, Pawel Laszczak wrote:
> From: Pawel Laszczak <pawell@...ence.com>
> 
> Patch puts content of cdnsp_gadget_pullup function inside
> spin_lock_irqsave and spin_lock_restore section.
> This construction is required here to keep the data consistency,
> otherwise some data can be changed e.g. from interrupt context.
> 
> Fixes: 3d82904559f4 ("usb: cdnsp: cdns3 Add main part of Cadence USBSSP DRD Driver")
> Reported-by: Ken (Jian) He <jianhe@...arella.com>
> cc: <stable@...r.kernel.org>
> Signed-off-by: Pawel Laszczak <pawell@...ence.com>
> ---
>  drivers/usb/cdns3/cdnsp-gadget.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/usb/cdns3/cdnsp-gadget.c b/drivers/usb/cdns3/cdnsp-gadget.c
> index f6d231760a6a..d0c040556984 100644
> --- a/drivers/usb/cdns3/cdnsp-gadget.c
> +++ b/drivers/usb/cdns3/cdnsp-gadget.c
> @@ -1544,8 +1544,10 @@ static int cdnsp_gadget_pullup(struct usb_gadget *gadget, int is_on)
>  {
>  	struct cdnsp_device *pdev = gadget_to_cdnsp(gadget);
>  	struct cdns *cdns = dev_get_drvdata(pdev->dev);
> +	unsigned long flags;
>  
>  	trace_cdnsp_pullup(is_on);
> +	spin_lock_irqsave(&pdev->lock, flags);

If the interrupt bottom half is pending, the consistent issue may still
exist, you may let the bottom half has finished first, eg: calling
disable_irq before spin_lock_irqsave.

Peter
>  
>  	if (!is_on) {
>  		cdnsp_reset_device(pdev);
> @@ -1553,6 +1555,9 @@ static int cdnsp_gadget_pullup(struct usb_gadget *gadget, int is_on)
>  	} else {
>  		cdns_set_vbus(cdns);
>  	}
> +
> +	spin_unlock_irqrestore(&pdev->lock, flags);
> +
>  	return 0;
>  }
>  
> -- 
> 2.25.1
> 

-- 

Thanks,
Peter Chen