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Date:   Thu, 17 Nov 2022 13:58:25 -0800
From:   Kees Cook <keescook@chromium.org>
To:     "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc:     linux-kernel@vger.kernel.org, patches@lists.linux.dev,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jakub Kicinski <kuba@kernel.org>,
        Russell King <linux@armlinux.org.uk>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Heiko Carstens <hca@linux.ibm.com>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Christoph =?iso-8859-1?Q?B=F6hmwalder?= 
        <christoph.boehmwalder@linbit.com>,
        Jani Nikula <jani.nikula@linux.intel.com>,
        Jason Gunthorpe <jgg@nvidia.com>,
        Sakari Ailus <sakari.ailus@linux.intel.com>,
        "Martin K . Petersen" <martin.petersen@oracle.com>,
        Theodore Ts'o <tytso@mit.edu>,
        Andreas Dilger <adilger.kernel@dilger.ca>,
        Jaegeuk Kim <jaegeuk@kernel.org>,
        Richard Weinberger <richard@nod.at>,
        "Darrick J . Wong" <djwong@kernel.org>,
        SeongJae Park <sj@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Andrew Morton <akpm@linux-foundation.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Helge Deller <deller@gmx.de>, netdev@vger.kernel.org,
        linux-crypto@vger.kernel.org, linux-block@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-media@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev,
        linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        linux-mmc@vger.kernel.org, linux-parisc@vger.kernel.org
Subject: Re: [PATCH v3 2/3] treewide: use get_random_u32_{above,below}()
 instead of manual loop
Message-ID: <202211171358.4B4E0E2F17@keescook>
References: <20221114164558.1180362-1-Jason@zx2c4.com>
 <20221117202906.2312482-1-Jason@zx2c4.com>
 <20221117202906.2312482-3-Jason@zx2c4.com>
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In-Reply-To: <20221117202906.2312482-3-Jason@zx2c4.com>
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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@linuxfoundation.org>
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

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

-- 
Kees Cook