linux-kernel - Re: [PATCH, RFC] random: introduce getrandom(2) system call

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Date:	Thu, 17 Jul 2014 12:33:30 -0700
From:	Greg KH <greg@...ah.com>
To:	Theodore Ts'o <tytso@....edu>
Cc:	linux-kernel@...r.kernel.org, linux-abi@...r.kernel.org,
	linux-crypto@...r.kernel.org, beck@...nbsd.org
Subject: Re: [PATCH, RFC] random: introduce getrandom(2) system call

On Thu, Jul 17, 2014 at 05:18:15AM -0400, Theodore Ts'o wrote:
> +SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count,
> +		unsigned int, flags)
> +{
> +	int r;
> +
> +	if (count > 256)
> +		return -EINVAL;
> +
> +	if (flags & GRND_RANDOM) {
> +		return _random_read(!(flags & GRND_BLOCK), buf, count);
> +	}
> +	if (flags & GRND_BLOCK) {
> +		r = wait_for_completion_interruptible(&urandom_initialized);
> +		if (r)
> +			return r;
> +	} else if (!completion_done(&urandom_initialized))
> +		return -EAGAIN;
> +	return urandom_read(NULL, buf, count, NULL);
> +}

You should fail if any other bits are set that you don't understand in
the flags value, to make it easier for newer kernels with more flags to
fail properly on old kernel releases.

thanks,

greg k-h
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