Re: binfmt_elf: use ELF_ET_DYN_BASE only for PIE breaks asan

[Kees Cook <keescook@google.com>]

On Mon, Aug 7, 2017 at 12:40 PM, Kostya Serebryany <kcc@google.com> wrote:
>
>
> On Mon, Aug 7, 2017 at 12:34 PM, Kees Cook <keescook@google.com> wrote:
>>
>> (To be clear, this subthread is for dealing with _future_ changes; I'm
>> already preparing the revert, which is in the other subthread.)
>>
>> On Mon, Aug 7, 2017 at 12:26 PM, Kostya Serebryany <kcc@google.com> wrote:
>> > Oh, a launcher (e.g. just using setarch) would be a huge pain to deploy.
>>
>> Would loading the executable into the mmap region work?
>
> This is beyond my knowledge. :(
> Could you explain?

PIE has a separate randomization base (before at 0x5555 5555 4000,
currently 0x1 0000 0000) from the mmap (DSO) area (0x7f00 0000
0000-ish). The primary reason to keep PIE separate from mmap is to
avoid leaking ASLR offsets between them, but if that's less of a
concern for *San, then we could just load PIE into the mmap region.

> If we can do this w/o a launcher (and w/o re-executing), we should try.

Let me think about the best way to do this...

-Kees

-- 
Kees Cook
Pixel Security

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