linux-kernel - Re: [PATCH] randomize_range: use random long instead of int

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Date:	Tue, 26 Jul 2016 02:18:30 +0000
From:	Jason Cooper <jason@...edaemon.net>
To:	william.c.roberts@...el.com
Cc:	linux-mm@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux@....linux.org.uk, akpm@...ux-foundation.org,
	keescook@...omium.org, tytso@....edu, arnd@...db.de,
	gregkh@...uxfoundation.org, catalin.marinas@....com,
	will.deacon@....com, ralf@...ux-mips.org, benh@...nel.crashing.org,
	paulus@...ba.org, mpe@...erman.id.au, davem@...emloft.net,
	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
	x86@...nel.org, viro@...iv.linux.org.uk, nnk@...gle.com,
	jeffv@...gle.com, salyzyn@...roid.com, dcashman@...roid.com
Subject: Re: [PATCH] randomize_range: use random long instead of int

Hi William, Kees,

On Mon, Jul 25, 2016 at 11:25:41AM -0700, william.c.roberts@...el.com wrote:
> From: William Roberts <william.c.roberts@...el.com>
> 
> Use a long when generating the random range rather than
> an int. This will produce better random distributions as
> well as matching all the types at hand.
> 
> Signed-off-by: William Roberts <william.c.roberts@...el.com>
> ---
>  drivers/char/random.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)

Upon further review, I think we should dig into this a little bit
deeper.  Standby, I'll post an RFC series shortly.

thx,

Jason.

> diff --git a/drivers/char/random.c b/drivers/char/random.c
> index 0158d3b..bbf11b5 100644
> --- a/drivers/char/random.c
> +++ b/drivers/char/random.c
> @@ -1837,7 +1837,8 @@ randomize_range(unsigned long start, unsigned long end, unsigned long len)
>  
>  	if (end <= start + len)
>  		return 0;
> -	return PAGE_ALIGN(get_random_int() % range + start);
> +
> +	return PAGE_ALIGN(get_random_long() % range + start);
>  }
>  
>  /* Interface for in-kernel drivers of true hardware RNGs.
> -- 
> 1.9.1
>