linux-kernel - Re: [PATCH v11] ARM: uncompress: Validate start of physical memory against passed DTB

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Date:   Sat, 12 Dec 2020 21:21:34 -0800
From:   Stephen Boyd <sboyd@...nel.org>
To:     Ard Biesheuvel <ardb@...nel.org>,
        Dmitry Osipenko <digetx@...il.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Linus Walleij <linus.walleij@...aro.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Nicolas Pitre <nico@...xnic.net>,
        Russell King <linux@...linux.org.uk>
Cc:     Arnd Bergmann <arnd@...db.de>, Eric Miao <eric.miao@...dia.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Lukasz Stelmach <l.stelmach@...sung.com>,
        Chris Brandt <chris.brandt@...esas.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Geert Uytterhoeven <geert+renesas@...der.be>
Subject: Re: [PATCH v11] ARM: uncompress: Validate start of physical memory against passed DTB

Quoting Geert Uytterhoeven (2020-12-10 01:32:01)
> diff --git a/arch/arm/boot/compressed/fdt_check_mem_start.c b/arch/arm/boot/compressed/fdt_check_mem_start.c
> new file mode 100644
> index 0000000000000000..e58c3a79c8a31ec4
> --- /dev/null
> +++ b/arch/arm/boot/compressed/fdt_check_mem_start.c
> @@ -0,0 +1,131 @@
[...]
> +
> +static uint64_t get_val(const fdt32_t *cells, uint32_t ncells)
> +{
> +       uint64_t r = 0;

This assignment is unnecessary?

> +
> +       r = fdt32_ld(cells);
> +       if (ncells > 1)
> +               r = (r << 32) | fdt32_ld(cells + 1);
> +
> +       return r;