Re: [PATCH] staging: comedi: use memdup_user

From	Joe Perches <joe@perches.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] staging: comedi: use memdup_user
Date	2017-04-29 04:00 +0200
Message-ID	<tBpPX-7Lk-3@gated-at.bofh.it> (permalink)
References	<tBpGh-7H8-5@gated-at.bofh.it> <tBpGh-7H8-3@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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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++) {

Thread

[PATCH] staging: comedi: use memdup_user Geliang Tang <geliangtang@gmail.com> - 2017-04-29 03:50 +0200
  Re: [PATCH] staging: comedi: use memdup_user Joe Perches <joe@perches.com> - 2017-04-29 04:00 +0200
    Re: [PATCH] staging: comedi: use memdup_user Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-29 07:20 +0200

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