linux-kernel - Re: [PATCH v3 2/3] treewide: use get_random_u32

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Message-ID: <202211171358.4B4E0E2F17@keescook>
Date:   Thu, 17 Nov 2022 13:58:25 -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 v3 2/3] treewide: use get_random_u32_{above,below}()
 instead of manual loop

On Thu, Nov 17, 2022 at 09:29:05PM +0100, Jason A. Donenfeld wrote:
> These cases were done with this Coccinelle:
> 
> @@
> expression E;
> identifier I;
> @@
> -   do {
>       ... when != I
> -     I = get_random_u32();
>       ... when != I
> -   } while (I > E);
> +   I = get_random_u32_below(E + 1);
> 
> @@
> expression E;
> identifier I;
> @@
> -   do {
>       ... when != I
> -     I = get_random_u32();
>       ... when != I
> -   } while (I >= E);
> +   I = get_random_u32_below(E);
> 
> @@
> expression E;
> identifier I;
> @@
> -   do {
>       ... when != I
> -     I = get_random_u32();
>       ... when != I
> -   } while (I < E);
> +   I = get_random_u32_above(E - 1);
> 
> @@
> expression E;
> identifier I;
> @@
> -   do {
>       ... when != I
> -     I = get_random_u32();
>       ... when != I
> -   } while (I <= E);
> +   I = get_random_u32_above(E);
> 
> @@
> identifier I;
> @@
> -   do {
>       ... when != I
> -     I = get_random_u32();
>       ... when != I
> -   } while (!I);
> +   I = get_random_u32_above(0);
> 
> @@
> identifier I;
> @@
> -   do {
>       ... when != I
> -     I = get_random_u32();
>       ... when != I
> -   } while (I == 0);
> +   I = get_random_u32_above(0);
> 
> @@
> expression E;
> @@
> - E + 1 + get_random_u32_below(U32_MAX - E)
> + get_random_u32_above(E)
> 
> Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook