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Date: Mon, 2 May 2016 16:15:38 +0200
From: Oleg Nesterov <oleg@redhat.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Jerome Glisse <j.glisse@gmail.com>, Hugh Dickins <hughd@google.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Alex Williamson <alex.williamson@redhat.com>,
        kirill.shutemov@linux.intel.com, linux-kernel@vger.kernel.org,
        "linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: Re: GUP guarantees wrt to userspace mappings redesign
Message-ID: <20160502141538.GA5961@redhat.com>
References: <20160428181726.GA2847@node.shutemov.name> <20160428125808.29ad59e5@t450s.home> <20160428232127.GL11700@redhat.com> <20160429005106.GB2847@node.shutemov.name> <20160428204542.5f2053f7@ul30vt.home> <20160429070611.GA4990@node.shutemov.name> <20160429163444.GM11700@redhat.com> <20160502104119.GA23305@node.shutemov.name> <20160502111513.GA4079@gmail.com> <20160502121402.GB23305@node.shutemov.name>
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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?

Oleg.