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

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Date:	Thu, 17 Jul 2014 12:57:07 +0200
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
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 Do, 2014-07-17 at 05:18 -0400, Theodore Ts'o wrote:
> SYNOPSIS
> 	#include <linux/random.h>
> 
> 	int getrandom(void *buf, size_t buflen, unsigned int flags);

Cool, I think the interface is sane.

Btw. couldn't libressl etc. fall back to binary_sysctl
kernel.random.uuid and seed with that as a last resort? We have it
available for few more years.

> +SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count,
> +		unsigned int, flags)
> +{
> +	int r;
> +
> +	if (count > 256)
> +		return -EINVAL;
> +

Why this "arbitrary" limitation? Couldn't we just check for > SSIZE_MAX
or to be more conservative to INT_MAX?

> +	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);
> +}
> +

Great, thanks Ted,
Hannes



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