Re: GUP guarantees wrt to userspace mappings redesign

From: Oleg Nesterov
Date: Mon May 02 2016 - 11:17:44 EST

I am sure I missed the problem, but...

On 05/02, Kirill A. Shutemov wrote:
> Quick look around:
> - I don't see any check page_count() around __replace_page() in uprobes,
> so it can easily replace pinned page.

Why it should? even if it races with get_user_pages_fast()... this doesn't
differ from the case when an application writes to MAP_PRIVATE non-anonymous
region, no?