Re: [PATCHv3 1/2] mm/gup: fix omission of check on FOLL_LONGTERM in get_user_pages_fast()

[Aneesh Kumar K.V]

Pingfan Liu <kernelfans@xxxxxxxxx> writes:

> As for FOLL_LONGTERM, it is checked in the slow path
> __gup_longterm_unlocked(). But it is not checked in the fast path, which
> means a possible leak of CMA page to longterm pinned requirement through
> this crack.

Shouldn't we disallow FOLL_LONGTERM with get_user_pages fastpath? W.r.t
dax check we need vma to ensure whether a long term pin is allowed or not.
If FOLL_LONGTERM is specified we should fallback to slow path.

-aneesh