linux-kernel - Re: [PATCH v2 3/3] treewide: use get_random_u32

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Message-ID: <202211161436.A45AD719A@keescook>
Date:   Wed, 16 Nov 2022 14:43:13 -0800
From:   Kees Cook <keescook@...omium.org>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     linux-kernel@...r.kernel.org, patches@...ts.linux.dev,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Christoph Böhmwalder 
        <christoph.boehmwalder@...bit.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        Theodore Ts'o <tytso@....edu>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        Richard Weinberger <richard@....at>,
        "Darrick J . Wong" <djwong@...nel.org>,
        SeongJae Park <sj@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Helge Deller <deller@....de>, netdev@...r.kernel.org,
        linux-crypto@...r.kernel.org, linux-block@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-media@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, loongarch@...ts.linux.dev,
        linux-mips@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-mmc@...r.kernel.org, linux-parisc@...r.kernel.org
Subject: Re: [PATCH v2 3/3] treewide: use get_random_u32_between() when
 possible

On Mon, Nov 14, 2022 at 05:45:58PM +0100, Jason A. Donenfeld wrote:
> -				(get_random_u32_below(1024) + 1) * PAGE_SIZE;
> +				get_random_u32_between(1, 1024 + 1) * PAGE_SIZE;

I really don't like "between". Can't this be named "inclusive" (and
avoid adding 1 everywhere, which seems ugly), or at least named
something less ambiguous?

> -		n = get_random_u32_below(100) + 1;
> +		n = get_random_u32_between(1, 101);

Because I find this much less readable. "Below 100" is clear: 0-99
inclusive, plus 1, so 1-100 inclusive. "Between 1 and 101" is not obvious
to me to mean: 1-100 inclusive.

These seem so much nicer:
	get_random_u32_inclusive(1, 1024)
	get_random_u32_inclusive(1, 100)

-- 
Kees Cook