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References: <20190417052247.17809-1-alex@ghiti.fr> <20190417052247.17809-3-alex@ghiti.fr>
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From:   Kees Cook <keescook@chromium.org>
Date:   Wed, 17 Apr 2019 23:32:17 -0500
Message-ID: <CAGXu5jKVa2YgAkWH1e26kxd2j6C4WsJ38+Z3K1z7JRvr_jDX6Q@mail.gmail.com>
Subject: Re: [PATCH v3 02/11] arm64: Make use of is_compat_task instead of
 hardcoding this test
To:     Alexandre Ghiti <alex@ghiti.fr>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Christoph Hellwig <hch@lst.de>,
        Russell King <linux@armlinux.org.uk>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Ralf Baechle <ralf@linux-mips.org>,
        Paul Burton <paul.burton@mips.com>,
        James Hogan <jhogan@kernel.org>,
        Palmer Dabbelt <palmer@sifive.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Luis Chamberlain <mcgrof@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        linux-mips@vger.kernel.org, linux-riscv@lists.infradead.org,
        "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
        Linux-MM <linux-mm@kvack.org>
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On Wed, Apr 17, 2019 at 12:25 AM Alexandre Ghiti <alex@ghiti.fr> wrote:
>
> Each architecture has its own way to determine if a task is a compat task,
> by using is_compat_task in arch_mmap_rnd, it allows more genericity and
> then it prepares its moving to mm/.
>
> Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>

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

-Kees

> ---
>  arch/arm64/mm/mmap.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c
> index 842c8a5fcd53..ed4f9915f2b8 100644
> --- a/arch/arm64/mm/mmap.c
> +++ b/arch/arm64/mm/mmap.c
> @@ -54,7 +54,7 @@ unsigned long arch_mmap_rnd(void)
>         unsigned long rnd;
>
>  #ifdef CONFIG_COMPAT
> -       if (test_thread_flag(TIF_32BIT))
> +       if (is_compat_task())
>                 rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1);
>         else
>  #endif
> --
> 2.20.1
>


-- 
Kees Cook