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
Date: Mon, 2 May 2016 19:41:14 +0200 [thread overview]
Message-ID: <20160502174114.GA15417@redhat.com> (raw)
In-Reply-To: <20160502180303.GA26252@node.shutemov.name>
On 05/02, Kirill A. Shutemov wrote:
>
> On Mon, May 02, 2016 at 06:22:11PM +0200, Oleg Nesterov wrote:
> > > 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.
> >
> > Yes... but I don't understand the problem space. I mean, I do not know why
> > this driver should expect this, how it can be broken, etc.
> >
> > I do not even understand why "initiated by other process" can make any
> > difference... Unless this driver somehow controls all threads which could
> > have this page mapped.
>
> Okay, my understanding is following:
>
> Some drivers (i.e. vfio) rely on get_user_page{,_fast}() to pin the memory
> and expect pinned pages to be mapped into userspace until the pin is gone.
> This memory is used to communicate between kernel and userspace.
Thanks Kirill.
Then I think uprobes should be fine,
> I don't think there's something to fix on uprobe side. It's part of
> debugging interface. Debuggers can be destructive, nothing new there.
Yes, exactly. And as for uprobes in particular, __replace_page() can
only be called of vma->vm_file and and the mapping is private/executable,
VM_MAYSHARE must not be set.
Unlikely userspace can read or write to this memory to communicate with
kernel or something else.
Thanks,
Oleg.
next prev parent reply other threads:[~2016-05-02 18:43 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
2016-05-02 16:22 ` Oleg Nesterov
2016-05-02 18:03 ` Kirill A. Shutemov
2016-05-02 17:41 ` Oleg Nesterov [this message]
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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