linux-kernel - Re: [PATCH] usbip: vudc: fix null pointer dereference on udc->lock

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Message-ID: <0e3059a0-1310-5d08-4623-f1cf34c52fc0@kernel.org>
Date:   Mon, 26 Feb 2018 09:40:25 -0700
From:   Shuah Khan <shuah@...nel.org>
To:     Colin King <colin.king@...onical.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org,
        Shuah Khan <shuahkh@....samsung.com>,
        Shuah Khan <shuah@...nel.org>
Subject: Re: [PATCH] usbip: vudc: fix null pointer dereference on udc->lock

On 02/22/2018 10:39 AM, Colin King wrote:
> From: Colin Ian King <colin.king@...onical.com>
> 
> Currently the driver attempts to spin lock on udc->lock before a NULL
> pointer check is performed on udc, hence there is a potential null
> pointer dereference on udc->lock.  Fix this by moving the null check
> on udc before the lock occurs.
> 
> Fixes: ea6873a45a22 ("usbip: vudc: Add SysFS infrastructure for VUDC")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  drivers/usb/usbip/vudc_sysfs.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/usbip/vudc_sysfs.c b/drivers/usb/usbip/vudc_sysfs.c
> index d86f72bbbb91..6dcd3ff655c3 100644
> --- a/drivers/usb/usbip/vudc_sysfs.c
> +++ b/drivers/usb/usbip/vudc_sysfs.c
> @@ -105,10 +105,14 @@ static ssize_t usbip_sockfd_store(struct device *dev, struct device_attribute *a
>  	if (rv != 0)
>  		return -EINVAL;
>  
> +	if (!udc) {
> +		dev_err(dev, "no device");
> +		return -ENODEV;
> +	}
>  	spin_lock_irqsave(&udc->lock, flags);
>  	/* Don't export what we don't have */
> -	if (!udc || !udc->driver || !udc->pullup) {
> -		dev_err(dev, "no device or gadget not bound");
> +	if (!udc->driver || !udc->pullup) {
> +		dev_err(dev, "gadget not bound");
>  		ret = -ENODEV;
>  		goto unlock;
>  	}
> 

Thanks for the patch. Looks good to me.

Acked-by: Shuah Khan <shuahkh@....samsung.com>

thanks,
-- Shuah