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Date: Mon, 26 Feb 2024 11:39:35 +0100 (CET)
From: Jiri Kosina <jikos@kernel.org>
To: Kees Cook <keescook@chromium.org>
cc: y0un9n132@gmail.com, Geert Uytterhoeven <geert@linux-m68k.org>, 
    Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, 
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    "H. Peter Anvin" <hpa@zytor.com>, Peter Zijlstra <peterz@infradead.org>, 
    Qi Zheng <zhengqi.arch@bytedance.com>, 
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    Christophe Leroy <christophe.leroy@csgroup.eu>, 
    Josh Poimboeuf <jpoimboe@kernel.org>, 
    "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, 
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    linux-hardening@vger.kernel.org
Subject: Re: [PATCH 1/2] x86: Increase brk randomness entropy on x86_64
In-Reply-To: <20240217062545.1631668-1-keescook@chromium.org>
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References: <20240217062035.work.493-kees@kernel.org> <20240217062545.1631668-1-keescook@chromium.org>
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On Fri, 16 Feb 2024, Kees Cook wrote:

> In commit c1d171a00294 ("x86: randomize brk"), arch_randomize_brk() was
> defined to use a 32MB range (13 bits of entropy), but was never increased
> when moving to 64-bit. The default arch_randomize_brk() uses 32MB for
> 32-bit tasks, and 1GB (18 bits of entropy) for 64-bit tasks. Update
> x86_64 to match the entropy used by arm64 and other 64-bit architectures.
> 
> Reported-by: y0un9n132@gmail.com
> Closes: https://lore.kernel.org/linux-hardening/CA+2EKTVLvc8hDZc+2Yhwmus=dzOUG5E4gV7ayCbu0MPJTZzWkw@mail.gmail.com/
> Signed-off-by: Kees Cook <keescook@chromium.org>

Wow, this is a pretty aged code indeed.

	Acked-by: Jiri Kosina <jkosina@suse.com>

Thanks,

-- 
Jiri Kosina
SUSE Labs