Re: [PATCH RFC] mm: protect suid binaries against rowhammer with copy-on-read mappings

[Konstantin Khlebnikov <khlebnikov@yandex-team.ru>]

On 18.03.2015 12:57, Kirill A. Shutemov wrote:
> On Wed, Mar 18, 2015 at 11:30:40AM +0300, Konstantin Khlebnikov wrote:
>> From: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
>>
>> Each user gets private copy of the code thus nobody will be able to exploit
>> pages in the page cache. This works for statically-linked binaries. Shared
>> libraries are still vulnerable, but setting suid bit will protect them too.
>
> Hm. Do we have suid/sgid semantic defiend for non-executables?
>
> To me we should do this for all file private mappings of the suid process
> or don't do it at all.

Yeah, this patch doesn't provide full protection.
That's just a proof-of-concept.

>
> And what about forked suid process which dropped privilages. We still have
> code pages shared.

User can get access to that private copy later but new suid
applications will get their own copy at exec.
Original page-cache pages are never exposed in pte.

>
> I don't think it worth it. The only right way to fix the problem is ECC
> memory.
>

ECC seems good protection until somebody figure out how to break it too.

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