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From:   "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
To:     Pingfan Liu <kernelfans@gmail.com>, linux-mm@kvack.org
Cc:     Pingfan Liu <kernelfans@gmail.com>,
        Ira Weiny <ira.weiny@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mike Rapoport <rppt@linux.ibm.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Matthew Wilcox <willy@infradead.org>,
        John Hubbard <jhubbard@nvidia.com>,
        Keith Busch <keith.busch@intel.com>,
        Christoph Hellwig <hch@infradead.org>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCHv3 1/2] mm/gup: fix omission of check on FOLL_LONGTERM in get_user_pages_fast()
In-Reply-To: <1559725820-26138-1-git-send-email-kernelfans@gmail.com>
References: <1559725820-26138-1-git-send-email-kernelfans@gmail.com>
Date:   Tue, 11 Jun 2019 21:45:31 +0530
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Pingfan Liu <kernelfans@gmail.com> 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