Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1392389

Re: GUP guarantees wrt to userspace mappings redesign

From Oleg Nesterov <oleg@redhat.com>
Newsgroups linux.kernel
Subject Re: GUP guarantees wrt to userspace mappings redesign
Date 2016-05-02 19:30 +0200
Message-ID <rupPu-7D1-41@gated-at.bofh.it> (permalink)
References (5 earlier) <rujAl-1I4-5@gated-at.bofh.it> <ruk3o-2eU-3@gated-at.bofh.it> <rukZs-3a6-23@gated-at.bofh.it> <runNE-5Nz-9@gated-at.bofh.it> <ruoTp-6N4-31@gated-at.bofh.it>
Organization linux.* mail to news gateway

Show all headers | View raw

On 05/02, Kirill A. Shutemov wrote:
>
> On Mon, May 02, 2016 at 04:15:38PM +0200, Oleg Nesterov wrote:
> > >
> > >  - 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.

Yes. Just like gdb can insert a breakpoint into the read-only executable vma.

> 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.

Oleg.

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[BUG] vfio device assignment regression with THP ref counting  redesign Alex Williamson <alex.williamson@redhat.com> - 2016-04-28 18:30 +0200
  Re: [BUG] vfio device assignment regression with THP ref counting  redesign "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-04-28 20:20 +0200
    Re: [BUG] vfio device assignment regression with THP ref counting  redesign Alex Williamson <alex.williamson@redhat.com> - 2016-04-28 21:00 +0200
      Re: [BUG] vfio device assignment regression with THP ref counting  redesign Andrea Arcangeli <aarcange@redhat.com> - 2016-04-29 01:30 +0200
        Re: [BUG] vfio device assignment regression with THP ref counting  redesign Alex Williamson <alex.williamson@redhat.com> - 2016-04-29 02:50 +0200
        Re: [BUG] vfio device assignment regression with THP ref counting  redesign "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-04-29 03:00 +0200
          Re: [BUG] vfio device assignment regression with THP ref counting  redesign Alex Williamson <alex.williamson@redhat.com> - 2016-04-29 04:50 +0200
            Re: [BUG] vfio device assignment regression with THP ref counting  redesign "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-04-29 09:10 +0200
              Re: [BUG] vfio device assignment regression with THP ref counting  redesign Alex Williamson <alex.williamson@redhat.com> - 2016-04-29 17:20 +0200
              Re: [BUG] vfio device assignment regression with THP ref counting  redesign Andrea Arcangeli <aarcange@redhat.com> - 2016-04-29 18:40 +0200
                Re: [BUG] vfio device assignment regression with THP ref counting  redesign Alex Williamson <alex.williamson@redhat.com> - 2016-04-30 00:40 +0200
                Re: [BUG] vfio device assignment regression with THP ref counting  redesign "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-05-02 12:50 +0200
                Re: [BUG] vfio device assignment regression with THP ref counting  redesign Jerome Glisse <j.glisse@gmail.com> - 2016-05-02 13:20 +0200
                GUP guarantees wrt to userspace mappings redesign "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-05-02 14:20 +0200
                Re: GUP guarantees wrt to userspace mappings redesign Jerome Glisse <j.glisse@gmail.com> - 2016-05-02 15:40 +0200
                Re: GUP guarantees wrt to userspace mappings "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-05-02 17:10 +0200
                Re: GUP guarantees wrt to userspace mappings Jerome Glisse <j.glisse@gmail.com> - 2016-05-02 17:30 +0200
                Re: GUP guarantees wrt to userspace mappings "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-05-02 18:20 +0200
                Re: GUP guarantees wrt to userspace mappings Andrea Arcangeli <aarcange@redhat.com> - 2016-05-02 21:20 +0200
                Re: GUP guarantees wrt to userspace mappings Andrea Arcangeli <aarcange@redhat.com> - 2016-05-02 21:20 +0200
                Re: GUP guarantees wrt to userspace mappings Andrea Arcangeli <aarcange@redhat.com> - 2016-05-02 21:10 +0200
                Re: GUP guarantees wrt to userspace mappings redesign Oleg Nesterov <oleg@redhat.com> - 2016-05-02 17:20 +0200
                Re: GUP guarantees wrt to userspace mappings redesign "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-05-02 18:30 +0200
                Re: GUP guarantees wrt to userspace mappings redesign Oleg Nesterov <oleg@redhat.com> - 2016-05-02 19:30 +0200
                Re: GUP guarantees wrt to userspace mappings redesign "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-05-02 20:10 +0200
                Re: GUP guarantees wrt to userspace mappings redesign Oleg Nesterov <oleg@redhat.com> - 2016-05-02 20:50 +0200
                Re: GUP guarantees wrt to userspace mappings redesign Andrea Arcangeli <aarcange@redhat.com> - 2016-05-02 21:00 +0200
                Re: [BUG] vfio device assignment regression with THP ref counting  redesign Andrea Arcangeli <aarcange@redhat.com> - 2016-05-02 17:30 +0200
                Re: [BUG] vfio device assignment regression with THP ref counting  redesign "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-05-02 18:10 +0200
                Re: [BUG] vfio device assignment regression with THP ref counting  redesign Andrea Arcangeli <aarcange@redhat.com> - 2016-05-02 20:10 +0200
                Re: [BUG] vfio device assignment regression with THP ref counting  redesign Alex Williamson <alex.williamson@redhat.com> - 2016-05-05 03:20 +0200
                Re: [BUG] vfio device assignment regression with THP ref counting  redesign Andrea Arcangeli <aarcange@redhat.com> - 2016-05-05 16:40 +0200
                Re: [BUG] vfio device assignment regression with THP ref counting  redesign Andrea Arcangeli <aarcange@redhat.com> - 2016-05-05 17:10 +0200
                Re: [BUG] vfio device assignment regression with THP ref counting  redesign "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-05-05 17:20 +0200
                Re: [BUG] vfio device assignment regression with THP ref counting  redesign Andrea Arcangeli <aarcange@redhat.com> - 2016-05-05 17:30 +0200
                Re: [BUG] vfio device assignment regression with THP ref counting  redesign "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-05-06 09:30 +0200

csiph-web