From: Peter Xu <peterx@redhat.com>
To: Mike Rapoport <rppt@linux.ibm.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
David Hildenbrand <david@redhat.com>,
Hugh Dickins <hughd@google.com>, Maya Gokhale <gokhale2@llnl.gov>,
Jerome Glisse <jglisse@redhat.com>,
Pavel Emelyanov <xemul@virtuozzo.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Martin Cracauer <cracauer@cons.org>, Shaohua Li <shli@fb.com>,
Marty McFadden <mcfadden8@llnl.gov>,
Andrea Arcangeli <aarcange@redhat.com>,
Mike Kravetz <mike.kravetz@oracle.com>,
Denis Plotnikov <dplotnikov@virtuozzo.com>,
Mike Rapoport <rppt@linux.vnet.ibm.com>,
Mel Gorman <mgorman@suse.de>,
"Kirill A . Shutemov" <kirill@shutemov.name>,
"Dr . David Alan Gilbert" <dgilbert@redhat.com>,
Rik van Riel <riel@redhat.com>
Subject: Re: [PATCH v2 20/26] userfaultfd: wp: support write protection for userfault vma range
Date: Tue, 26 Feb 2019 15:20:28 +0800 [thread overview]
Message-ID: <20190226072027.GK13653@xz-x1> (raw)
In-Reply-To: <20190226064347.GB5873@rapoport-lnx>
On Tue, Feb 26, 2019 at 08:43:47AM +0200, Mike Rapoport wrote:
> On Tue, Feb 26, 2019 at 02:06:27PM +0800, Peter Xu wrote:
> > On Mon, Feb 25, 2019 at 10:52:34PM +0200, Mike Rapoport wrote:
> > > On Tue, Feb 12, 2019 at 10:56:26AM +0800, Peter Xu wrote:
> > > > From: Shaohua Li <shli@fb.com>
> > > >
> > > > Add API to enable/disable writeprotect a vma range. Unlike mprotect,
> > > > this doesn't split/merge vmas.
> > > >
> > > > Cc: Andrea Arcangeli <aarcange@redhat.com>
> > > > Cc: Rik van Riel <riel@redhat.com>
> > > > Cc: Kirill A. Shutemov <kirill@shutemov.name>
> > > > Cc: Mel Gorman <mgorman@suse.de>
> > > > Cc: Hugh Dickins <hughd@google.com>
> > > > Cc: Johannes Weiner <hannes@cmpxchg.org>
> > > > Signed-off-by: Shaohua Li <shli@fb.com>
> > > > Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
> > > > [peterx:
> > > > - use the helper to find VMA;
> > > > - return -ENOENT if not found to match mcopy case;
> > > > - use the new MM_CP_UFFD_WP* flags for change_protection
> > > > - check against mmap_changing for failures]
> > > > Signed-off-by: Peter Xu <peterx@redhat.com>
> > > > ---
> > > > include/linux/userfaultfd_k.h | 3 ++
> > > > mm/userfaultfd.c | 54 +++++++++++++++++++++++++++++++++++
> > > > 2 files changed, 57 insertions(+)
> > > >
> > > > diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
> > > > index 765ce884cec0..8f6e6ed544fb 100644
> > > > --- a/include/linux/userfaultfd_k.h
> > > > +++ b/include/linux/userfaultfd_k.h
> > > > @@ -39,6 +39,9 @@ extern ssize_t mfill_zeropage(struct mm_struct *dst_mm,
> > > > unsigned long dst_start,
> > > > unsigned long len,
> > > > bool *mmap_changing);
> > > > +extern int mwriteprotect_range(struct mm_struct *dst_mm,
> > > > + unsigned long start, unsigned long len,
> > > > + bool enable_wp, bool *mmap_changing);
> > > >
> > > > /* mm helpers */
> > > > static inline bool is_mergeable_vm_userfaultfd_ctx(struct vm_area_struct *vma,
> > > > diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
> > > > index fefa81c301b7..529d180bb4d7 100644
> > > > --- a/mm/userfaultfd.c
> > > > +++ b/mm/userfaultfd.c
> > > > @@ -639,3 +639,57 @@ ssize_t mfill_zeropage(struct mm_struct *dst_mm, unsigned long start,
> > > > {
> > > > return __mcopy_atomic(dst_mm, start, 0, len, true, mmap_changing, 0);
> > > > }
> > > > +
> > > > +int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start,
> > > > + unsigned long len, bool enable_wp, bool *mmap_changing)
> > > > +{
> > > > + struct vm_area_struct *dst_vma;
> > > > + pgprot_t newprot;
> > > > + int err;
> > > > +
> > > > + /*
> > > > + * Sanitize the command parameters:
> > > > + */
> > > > + BUG_ON(start & ~PAGE_MASK);
> > > > + BUG_ON(len & ~PAGE_MASK);
> > > > +
> > > > + /* Does the address range wrap, or is the span zero-sized? */
> > > > + BUG_ON(start + len <= start);
> > >
> > > I'd replace these BUG_ON()s with
> > >
> > > if (WARN_ON())
> > > return -EINVAL;
> >
> > I believe BUG_ON() is used because these parameters should have been
> > checked in userfaultfd_writeprotect() already by the common
> > validate_range() even before calling mwriteprotect_range(). So I'm
> > fine with the WARN_ON() approach but I'd slightly prefer to simply
> > keep the patch as is to keep Jerome's r-b if you won't disagree. :)
>
> Right, userfaultfd_writeprotect() should check these parameters and if it
> didn't it was a bug indeed. But still, it's not severe enough to crash the
> kernel.
>
> I hope Jerome wouldn't mind to keep his r-b with s/BUG_ON/WARN_ON ;-)
>
> With this change you can also add
>
> Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Thanks! Though before I change anything... please note that the
BUG_ON()s are really what we've done in existing MISSING code. One
example is userfaultfd_copy() which did validate_range() first, then
in __mcopy_atomic() we've used BUG_ON()s. They make sense to me
becauase userspace should never be able to trigger it. And if we
really want to change the BUG_ON()s in this patch, IMHO we probably
want to change the other BUG_ON()s as well, then that can be a
standalone patch or patchset to address another issue...
(and if we really want to use WARN_ON, I would prefer WARN_ON_ONCE, or
directly return the errors to avoid DOS).
I'll see how you'd prefer to see how I should move on with this patch.
Thanks,
--
Peter Xu
next prev parent reply other threads:[~2019-02-26 7:20 UTC|newest]
Thread overview: 113+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-12 2:56 [PATCH v2 00/26] userfaultfd: write protection support Peter Xu
2019-02-12 2:56 ` [PATCH v2 01/26] mm: gup: rename "nonblocking" to "locked" where proper Peter Xu
2019-02-21 15:17 ` Jerome Glisse
2019-02-22 3:42 ` Peter Xu
2019-02-12 2:56 ` [PATCH v2 02/26] mm: userfault: return VM_FAULT_RETRY on signals Peter Xu
2019-02-21 15:29 ` Jerome Glisse
2019-02-22 3:51 ` Peter Xu
2019-02-12 2:56 ` [PATCH v2 03/26] userfaultfd: don't retake mmap_sem to emulate NOPAGE Peter Xu
2019-02-21 15:34 ` Jerome Glisse
2019-02-12 2:56 ` [PATCH v2 04/26] mm: allow VM_FAULT_RETRY for multiple times Peter Xu
2019-02-13 3:34 ` Peter Xu
2019-02-20 11:48 ` Peter Xu
2019-02-21 8:56 ` [PATCH v2.1 " Peter Xu
2019-02-21 15:53 ` Jerome Glisse
2019-02-22 4:25 ` Peter Xu
2019-02-22 15:11 ` Jerome Glisse
2019-02-25 6:19 ` Peter Xu
2019-02-12 2:56 ` [PATCH v2 05/26] mm: gup: " Peter Xu
2019-02-21 16:06 ` Jerome Glisse
2019-02-22 4:41 ` Peter Xu
2019-02-22 15:13 ` Jerome Glisse
2019-02-12 2:56 ` [PATCH v2 06/26] userfaultfd: wp: add helper for writeprotect check Peter Xu
2019-02-21 16:07 ` Jerome Glisse
2019-02-25 15:41 ` Mike Rapoport
2019-02-12 2:56 ` [PATCH v2 07/26] userfaultfd: wp: hook userfault handler to write protection fault Peter Xu
2019-02-21 16:25 ` Jerome Glisse
2019-02-25 15:43 ` Mike Rapoport
2019-02-12 2:56 ` [PATCH v2 08/26] userfaultfd: wp: add WP pagetable tracking to x86 Peter Xu
2019-02-21 17:20 ` Jerome Glisse
2019-02-25 15:48 ` Mike Rapoport
2019-02-12 2:56 ` [PATCH v2 09/26] userfaultfd: wp: userfaultfd_pte/huge_pmd_wp() helpers Peter Xu
2019-02-21 17:21 ` Jerome Glisse
2019-02-25 17:12 ` Mike Rapoport
2019-02-12 2:56 ` [PATCH v2 10/26] userfaultfd: wp: add UFFDIO_COPY_MODE_WP Peter Xu
2019-02-21 17:29 ` Jerome Glisse
2019-02-22 7:11 ` Peter Xu
2019-02-22 15:15 ` Jerome Glisse
2019-02-25 6:45 ` Peter Xu
2019-02-25 15:58 ` Mike Rapoport
2019-02-26 5:09 ` Peter Xu
2019-02-26 8:28 ` Mike Rapoport
2019-02-12 2:56 ` [PATCH v2 11/26] mm: merge parameters for change_protection() Peter Xu
2019-02-21 17:32 ` Jerome Glisse
2019-02-12 2:56 ` [PATCH v2 12/26] userfaultfd: wp: apply _PAGE_UFFD_WP bit Peter Xu
2019-02-21 17:44 ` Jerome Glisse
2019-02-22 7:31 ` Peter Xu
2019-02-22 15:17 ` Jerome Glisse
2019-02-25 18:00 ` Mike Rapoport
2019-02-12 2:56 ` [PATCH v2 13/26] mm: export wp_page_copy() Peter Xu
2019-02-21 17:44 ` Jerome Glisse
2019-02-12 2:56 ` [PATCH v2 14/26] userfaultfd: wp: handle COW properly for uffd-wp Peter Xu
2019-02-21 18:04 ` Jerome Glisse
2019-02-22 8:46 ` Peter Xu
2019-02-22 15:35 ` Jerome Glisse
2019-02-25 7:13 ` Peter Xu
2019-02-25 15:32 ` Jerome Glisse
2019-02-12 2:56 ` [PATCH v2 15/26] userfaultfd: wp: drop _PAGE_UFFD_WP properly when fork Peter Xu
2019-02-21 18:06 ` Jerome Glisse
2019-02-22 9:09 ` Peter Xu
2019-02-22 15:36 ` Jerome Glisse
2019-02-25 18:19 ` Mike Rapoport
2019-02-12 2:56 ` [PATCH v2 16/26] userfaultfd: wp: add pmd_swp_*uffd_wp() helpers Peter Xu
2019-02-21 18:07 ` Jerome Glisse
2019-02-25 18:20 ` Mike Rapoport
2019-02-12 2:56 ` [PATCH v2 17/26] userfaultfd: wp: support swap and page migration Peter Xu
2019-02-21 18:16 ` Jerome Glisse
2019-02-25 7:48 ` Peter Xu
2019-02-25 18:28 ` Mike Rapoport
2019-02-12 2:56 ` [PATCH v2 18/26] khugepaged: skip collapse if uffd-wp detected Peter Xu
2019-02-21 18:17 ` Jerome Glisse
2019-02-25 18:50 ` Mike Rapoport
2019-02-12 2:56 ` [PATCH v2 19/26] userfaultfd: introduce helper vma_find_uffd Peter Xu
2019-02-21 18:19 ` Jerome Glisse
2019-02-25 20:48 ` Mike Rapoport
2019-02-12 2:56 ` [PATCH v2 20/26] userfaultfd: wp: support write protection for userfault vma range Peter Xu
2019-02-21 18:23 ` Jerome Glisse
2019-02-25 8:16 ` Peter Xu
2019-02-25 20:52 ` Mike Rapoport
2019-02-26 6:06 ` Peter Xu
2019-02-26 6:43 ` Mike Rapoport
2019-02-26 7:20 ` Peter Xu [this message]
2019-02-26 7:46 ` Mike Rapoport
2019-02-26 7:54 ` Peter Xu
2019-02-12 2:56 ` [PATCH v2 21/26] userfaultfd: wp: add the writeprotect API to userfaultfd ioctl Peter Xu
2019-02-21 18:28 ` Jerome Glisse
2019-02-25 8:31 ` Peter Xu
2019-02-25 21:03 ` Mike Rapoport
2019-02-26 6:30 ` Peter Xu
2019-02-12 2:56 ` [PATCH v2 22/26] userfaultfd: wp: enabled write protection in userfaultfd API Peter Xu
2019-02-21 18:29 ` Jerome Glisse
2019-02-25 8:34 ` Peter Xu
2019-02-12 2:56 ` [PATCH v2 23/26] userfaultfd: wp: don't wake up when doing write protect Peter Xu
2019-02-21 18:36 ` Jerome Glisse
2019-02-25 8:58 ` Peter Xu
2019-02-25 21:15 ` Mike Rapoport
2019-02-25 21:09 ` Mike Rapoport
2019-02-26 6:24 ` Peter Xu
2019-02-26 7:29 ` Mike Rapoport
2019-02-26 7:41 ` Peter Xu
2019-02-26 8:00 ` Mike Rapoport
2019-02-28 2:47 ` Peter Xu
2019-02-26 8:00 ` Mike Rapoport
2019-02-12 2:56 ` [PATCH v2 24/26] userfaultfd: wp: UFFDIO_REGISTER_MODE_WP documentation update Peter Xu
2019-02-21 18:38 ` Jerome Glisse
2019-02-25 21:19 ` Mike Rapoport
2019-02-26 6:53 ` Peter Xu
2019-02-26 7:04 ` Mike Rapoport
2019-02-26 7:42 ` Peter Xu
2019-02-12 2:56 ` [PATCH v2 25/26] userfaultfd: selftests: refactor statistics Peter Xu
2019-02-26 6:50 ` Mike Rapoport
2019-02-12 2:56 ` [PATCH v2 26/26] userfaultfd: selftests: add write-protect test Peter Xu
2019-02-26 6:58 ` Mike Rapoport
2019-02-26 7:52 ` Peter Xu
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