Re: binfmt_elf: use ELF_ET_DYN_BASE only for PIE breaks asan

[Kees Cook <keescook@google.com>]

On Mon, Aug 7, 2017 at 12:05 PM, Kostya Serebryany <kcc@google.com> wrote:
>
>
> On Mon, Aug 7, 2017 at 11:59 AM, Kees Cook <keescook@google.com> wrote:
>>
>> On Mon, Aug 7, 2017 at 11:56 AM, Kostya Serebryany <kcc@google.com> wrote:
>> > Is it possible to implement some userspace<=>kernel interface that will
>> > allow applications (sanitizers)
>> > to request *fixed* address ranges from the kernel at startup (so that
>> > the
>> > kernel couldn't refuse)?
>>
>> Wouldn't building non-PIE accomplish this?
>
>
> Well, many asan users do need PIE.
> Then, non-PIE only applies to the main executable, all DSOs are still
> PIC and the old change that moved DSOs from 0x7fff to 0x5555 caused us quite
> a bit of trouble too, even w/o PIE

Hm? You can build non-PIE executables leaving all the DSOs PIC.

If what you want is to entirely disable userspace ASLR under *San, you
can just set the ADDR_NO_RANDOMIZE personality flag.

-Kees

-- 
Kees Cook
Pixel Security

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