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Date:   Tue, 17 Nov 2020 16:54:55 +0000
From:   Matthew Wilcox <willy@infradead.org>
To:     Topi Miettinen <toiwoton@gmail.com>
Cc:     linux-hardening@vger.kernel.org, akpm@linux-foundation.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Jann Horn <jannh@google.com>,
        Kees Cook <keescook@chromium.org>,
        Mike Rapoport <rppt@kernel.org>
Subject: Re: [PATCH v4] mm: Optional full ASLR for mmap() and mremap()
Message-ID: <20201117165455.GN29991@casper.infradead.org>
References: <20201026160518.9212-1-toiwoton@gmail.com>
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On Mon, Oct 26, 2020 at 06:05:18PM +0200, Topi Miettinen wrote:
> Writing a new value of 3 to /proc/sys/kernel/randomize_va_space
> enables full randomization of memory mappings created with mmap(NULL,
> ...). With 2, the base of the VMA used for such mappings is random,
> but the mappings are created in predictable places within the VMA and
> in sequential order. With 3, new VMAs are created to fully randomize
> the mappings. Also mremap(..., MREMAP_MAYMOVE) will move the mappings
> even if not necessary.

Is this worth it?

https://www.ndss-symposium.org/ndss2017/ndss-2017-programme/aslrcache-practical-cache-attacks-mmu/