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From: Evgenii Stepanov <eugenis@google.com>
Date: Mon, 7 Aug 2017 11:51:20 -0700
Message-ID: <CAFKCwrgp6HDdNJoAUwVdg7szJhZSj26NXF38UOJpp7tWxoXZUg@mail.gmail.com>
Subject: Re: binfmt_elf: use ELF_ET_DYN_BASE only for PIE breaks asan
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Sender: owner-linux-mm@kvack.org
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To: Kees Cook <keescook@google.com>
Cc: Kostya Serebryany <kcc@google.com>, Dmitry Vyukov <dvyukov@google.com>, Daniel Micay <danielmicay@gmail.com>, Michal Hocko <mhocko@kernel.org>, Andrew Morton <akpm@linux-foundation.org>, "linux-mm@kvack.org" <linux-mm@kvack.org>, Rik van Riel <riel@redhat.com>, Reid Kleckner <rnk@google.com>, Peter Collingbourne <pcc@google.com>

On Mon, Aug 7, 2017 at 11:40 AM, Kees Cook <keescook@google.com> wrote:
> On Mon, Aug 7, 2017 at 11:36 AM, Evgenii Stepanov <eugenis@google.com> wrote:
>> MSan is 64-bit only and does not allow any mappings _outside_ of these regions:
>> 000000000000 - 010000000000 app-1
>> 510000000000 - 600000000000 app-2
>> 700000000000 - 800000000000 app-3
>>
>> https://github.com/google/sanitizers/issues/579
>>
>> It sounds like the ELF_ET_DYN_BASE change should not break MSan.
>
> Hah, so the proposed move to 0x1000 8000 0000 for ASan would break
> MSan. Lovely! :P

That's unfortunate.
This will not help existing binaries, but going forward the mapping
can be adjusted at runtime to anything like
000000000000 .. A
500000000000 + A .. 600000000000
700000000000 .. 800000000000
i.e. we can look at where the binary is mapped and set A to anything
in the range of [0, 1000 0000 0000). That's still not compatible with
0x1000 8000 0000 though.

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