From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Oleg Nesterov <oleg@redhat.com>
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
Date: Mon, 2 May 2016 19:21:28 +0300 [thread overview]
Message-ID: <20160502162128.GF24419@node.shutemov.name> (raw)
In-Reply-To: <20160502141538.GA5961@redhat.com>
On Mon, May 02, 2016 at 04:15:38PM +0200, Oleg Nesterov wrote:
> 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?
< I know nothing about uprobes or ptrace in general >
I think the difference is that the write is initiated by the process
itself, but IIUC __replace_page() can be initiated by other process, so
it's out of control of the application.
So we have pages pinned by a driver and the driver expects the pinned
pages to be mapped into userspace, then __replace_page() kicks in and put
different page there -- driver's expectation is broken.
--
Kirill A. Shutemov
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next prev parent reply other threads:[~2016-05-02 16:21 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-28 16:20 [BUG] vfio device assignment regression with THP ref counting redesign Alex Williamson
2016-04-28 18:17 ` Kirill A. Shutemov
2016-04-28 18:58 ` Alex Williamson
2016-04-28 23:21 ` Andrea Arcangeli
2016-04-29 0:44 ` Alex Williamson
2016-04-29 0:51 ` Kirill A. Shutemov
2016-04-29 2:45 ` Alex Williamson
2016-04-29 7:06 ` Kirill A. Shutemov
2016-04-29 15:12 ` Alex Williamson
2016-04-29 16:34 ` Andrea Arcangeli
2016-04-29 22:34 ` Alex Williamson
2016-05-02 10:41 ` Kirill A. Shutemov
2016-05-02 11:15 ` Jerome Glisse
2016-05-02 12:14 ` GUP guarantees wrt to userspace mappings redesign Kirill A. Shutemov
2016-05-02 13:39 ` Jerome Glisse
2016-05-02 15:00 ` GUP guarantees wrt to userspace mappings Kirill A. Shutemov
2016-05-02 15:22 ` Jerome Glisse
2016-05-02 16:12 ` Kirill A. Shutemov
2016-05-02 19:14 ` Andrea Arcangeli
2016-05-02 19:11 ` Andrea Arcangeli
2016-05-02 19:02 ` Andrea Arcangeli
2016-05-02 14:15 ` GUP guarantees wrt to userspace mappings redesign Oleg Nesterov
2016-05-02 16:21 ` Kirill A. Shutemov [this message]
2016-05-02 16:22 ` Oleg Nesterov
2016-05-02 18:03 ` Kirill A. Shutemov
2016-05-02 17:41 ` Oleg Nesterov
2016-05-02 18:56 ` Andrea Arcangeli
2016-05-02 15:23 ` [BUG] vfio device assignment regression with THP ref counting redesign Andrea Arcangeli
2016-05-02 16:00 ` Kirill A. Shutemov
2016-05-02 18:03 ` Andrea Arcangeli
2016-05-05 1:19 ` Alex Williamson
2016-05-05 14:39 ` Andrea Arcangeli
2016-05-05 15:09 ` Andrea Arcangeli
2016-05-05 15:11 ` Kirill A. Shutemov
2016-05-05 15:24 ` Andrea Arcangeli
2016-05-06 7:29 ` Kirill A. Shutemov
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