linux-kernel - Re: [PATCH] staging: comedi: use memdup

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Message-ID: <1493430812.1873.26.camel@perches.com>
Date:   Fri, 28 Apr 2017 18:53:32 -0700
From:   Joe Perches <joe@...ches.com>
To:     Geliang Tang <geliangtang@...il.com>,
        Ian Abbott <abbotti@....co.uk>,
        H Hartley Sweeten <hsweeten@...ionengravers.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arnd Bergmann <arnd@...db.de>
Cc:     devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: comedi: use memdup_user

On Sat, 2017-04-29 at 09:45 +0800, Geliang Tang wrote:
> Use memdup_user() helper instead of open-coding to simplify the code.

While I doubt this is a problem, this loses
the multiplication overflow check for
sizeof(*insns) * insnlist.n_isns

> diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
[]
> @@ -1450,22 +1450,14 @@ static int do_insnlist_ioctl(struct comedi_device *dev,
>  		return -EFAULT;
>  
>  	data = kmalloc_array(MAX_SAMPLES, sizeof(unsigned int), GFP_KERNEL);
> -	if (!data) {
> -		ret = -ENOMEM;
> -		goto error;
> -	}
> -
> -	insns = kcalloc(insnlist.n_insns, sizeof(*insns), GFP_KERNEL);
> -	if (!insns) {
> -		ret = -ENOMEM;
> -		goto error;
> -	}
> +	if (!data)
> +		return -ENOMEM;
>  
> -	if (copy_from_user(insns, insnlist.insns,
> -			   sizeof(*insns) * insnlist.n_insns)) {
> -		dev_dbg(dev->class_dev, "copy_from_user failed\n");
> -		ret = -EFAULT;
> -		goto error;
> +	insns = memdup_user(insnlist.insns, sizeof(*insns) * insnlist.n_insns);
> +	if (IS_ERR(insns)) {
> +		dev_dbg(dev->class_dev, "memdup_user failed\n");
> +		kfree(data);
> +		return PTR_ERR(insns);
>  	}
>  
>  	for (i = 0; i < insnlist.n_insns; i++) {