linux-kernel - Re: [PATCH] goku_udc: Add check for NULL in goku

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Date:   Fri, 3 Feb 2023 09:43:59 -0500
From:   Alan Stern <stern@...land.harvard.edu>
To:     Anastasia Belova <abelova@...ralinux.ru>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jakob Koschel <jakobkoschel@...il.com>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        lvc-project@...uxtesting.org
Subject: Re: [PATCH] goku_udc: Add check for NULL in goku_irq

On Fri, Feb 03, 2023 at 01:18:28PM +0300, Anastasia Belova wrote:
> Before dereferencing dev->driver check it for NULL.
> 
> If an interrupt handler is called after assigning
> NULL to dev->driver, but before resetting dev->int_enable,
> NULL-pointer will be dereferenced.

Wouldn't it be better just to set dev->driver to NULL _after_ resetting 
dev->int_enable?

Alan Stern

> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Anastasia Belova <abelova@...ralinux.ru>
> ---
>  drivers/usb/gadget/udc/goku_udc.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/gadget/udc/goku_udc.c b/drivers/usb/gadget/udc/goku_udc.c
> index bdc56b24b5c9..896bba8b47f1 100644
> --- a/drivers/usb/gadget/udc/goku_udc.c
> +++ b/drivers/usb/gadget/udc/goku_udc.c
> @@ -1616,8 +1616,9 @@ static irqreturn_t goku_irq(int irq, void *_dev)
>  pm_next:
>  		if (stat & INT_USBRESET) {		/* hub reset done */
>  			ACK(INT_USBRESET);
> -			INFO(dev, "USB reset done, gadget %s\n",
> -				dev->driver->driver.name);
> +			if (dev->driver)
> +				INFO(dev, "USB reset done, gadget %s\n",
> +					dev->driver->driver.name);
>  		}
>  		// and INT_ERR on some endpoint's crc/bitstuff/... problem
>  	}
> -- 
> 2.30.2
>