From: Peter Xu <peterx@redhat.com>
To: Jerome Glisse <jglisse@redhat.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Hugh Dickins <hughd@google.com>, Maya Gokhale <gokhale2@llnl.gov>,
Johannes Weiner <hannes@cmpxchg.org>,
Martin Cracauer <cracauer@cons.org>,
Denis Plotnikov <dplotnikov@virtuozzo.com>,
Shaohua Li <shli@fb.com>, Andrea Arcangeli <aarcange@redhat.com>,
Pavel Emelyanov <xemul@parallels.com>,
Mike Kravetz <mike.kravetz@oracle.com>,
Marty McFadden <mcfadden8@llnl.gov>,
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>
Subject: Re: [PATCH RFC 02/24] mm: userfault: return VM_FAULT_RETRY on signals
Date: Tue, 22 Jan 2019 14:10:37 +0800 [thread overview]
Message-ID: <20190122061037.GA14907@xz-x1> (raw)
In-Reply-To: <20190121154017.GA3711@redhat.com>
On Mon, Jan 21, 2019 at 10:40:18AM -0500, Jerome Glisse wrote:
> On Mon, Jan 21, 2019 at 03:57:00PM +0800, Peter Xu wrote:
> > There was a special path in handle_userfault() in the past that we'll
> > return a VM_FAULT_NOPAGE when we detected non-fatal signals when waiting
> > for userfault handling. We did that by reacquiring the mmap_sem before
> > returning. However that brings a risk in that the vmas might have
> > changed when we retake the mmap_sem and even we could be holding an
> > invalid vma structure. The problem was reported by syzbot.
>
> This is confusing this should be a patch on its own ie changes to
> fs/userfaultfd.c where you remove that path.
Sure I will.
>
> >
> > This patch removes the special path and we'll return a VM_FAULT_RETRY
> > with the common path even if we have got such signals. Then for all the
> > architectures that is passing in VM_FAULT_ALLOW_RETRY into
> > handle_mm_fault(), we check not only for SIGKILL but for all the rest of
> > userspace pending signals right after we returned from
> > handle_mm_fault().
> >
> > The idea comes from the upstream discussion between Linus and Andrea:
> >
> > https://lkml.org/lkml/2017/10/30/560
> >
> > (This patch contains a potential fix for a double-free of mmap_sem on
> > ARC architecture; please see https://lkml.org/lkml/2018/11/1/723 for
> > more information)
>
> This patch should only be about changing the return to userspace rule.
> Before this patch the arch fault handler returned to userspace only
> for fatal signal, after this patch it returns to userspace for any
> signal.
Ok. I'll make the first patch to do the signal changes, then the
second patch to remove the userfault path explicitly.
>
> It would be a lot better to have a fix for arc as a separate patch so
> that we can focus on reviewing only one thing.
I just noticed that it was fixed just a few days ago in commit
4d447455e73b. Then I'll just simply rebase to Linus master and use
the upstream fix, then I can drop this paragraph.
Thanks for the review!
--
Peter Xu
next prev parent reply other threads:[~2019-01-22 6:10 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-21 7:56 [PATCH RFC 00/24] userfaultfd: write protection support Peter Xu
2019-01-21 7:56 ` [PATCH RFC 01/24] mm: gup: rename "nonblocking" to "locked" where proper Peter Xu
2019-01-21 10:20 ` Mike Rapoport
2019-01-21 7:57 ` [PATCH RFC 02/24] mm: userfault: return VM_FAULT_RETRY on signals Peter Xu
2019-01-21 15:40 ` Jerome Glisse
2019-01-22 6:10 ` Peter Xu [this message]
2019-01-21 7:57 ` [PATCH RFC 03/24] mm: allow VM_FAULT_RETRY for multiple times Peter Xu
2019-01-21 15:55 ` Jerome Glisse
2019-01-22 8:22 ` Peter Xu
2019-01-22 16:53 ` Jerome Glisse
2019-01-23 2:12 ` Peter Xu
2019-01-23 2:39 ` Jerome Glisse
2019-01-24 5:45 ` Peter Xu
2019-01-21 7:57 ` [PATCH RFC 04/24] mm: gup: " Peter Xu
2019-01-21 16:24 ` Jerome Glisse
2019-01-24 7:05 ` Peter Xu
2019-01-24 15:34 ` Jerome Glisse
2019-01-25 2:49 ` Peter Xu
2019-01-21 7:57 ` [PATCH RFC 05/24] userfaultfd: wp: add helper for writeprotect check Peter Xu
2019-01-21 10:23 ` Mike Rapoport
2019-01-22 8:31 ` Peter Xu
2019-01-21 7:57 ` [PATCH RFC 06/24] userfaultfd: wp: support write protection for userfault vma range Peter Xu
2019-01-21 10:20 ` Mike Rapoport
2019-01-22 8:55 ` Peter Xu
2019-01-21 14:05 ` Jerome Glisse
2019-01-22 9:39 ` Peter Xu
2019-01-22 17:02 ` Jerome Glisse
2019-01-23 2:17 ` Peter Xu
2019-01-23 2:43 ` Jerome Glisse
2019-01-24 5:47 ` Peter Xu
2019-01-21 7:57 ` [PATCH RFC 07/24] userfaultfd: wp: add the writeprotect API to userfaultfd ioctl Peter Xu
2019-01-21 10:42 ` Mike Rapoport
2019-01-24 4:56 ` Peter Xu
2019-01-24 7:27 ` Mike Rapoport
2019-01-24 9:28 ` Peter Xu
2019-01-25 7:54 ` Mike Rapoport
2019-01-25 10:12 ` Peter Xu
2019-01-21 7:57 ` [PATCH RFC 08/24] userfaultfd: wp: hook userfault handler to write protection fault Peter Xu
2019-01-21 7:57 ` [PATCH RFC 09/24] userfaultfd: wp: enabled write protection in userfaultfd API Peter Xu
2019-01-21 7:57 ` [PATCH RFC 10/24] userfaultfd: wp: add WP pagetable tracking to x86 Peter Xu
2019-01-21 15:09 ` Jerome Glisse
2019-01-24 5:16 ` Peter Xu
2019-01-24 15:40 ` Jerome Glisse
2019-01-25 3:30 ` Peter Xu
2019-01-21 7:57 ` [PATCH RFC 11/24] userfaultfd: wp: userfaultfd_pte/huge_pmd_wp() helpers Peter Xu
2019-01-21 7:57 ` [PATCH RFC 12/24] userfaultfd: wp: add UFFDIO_COPY_MODE_WP Peter Xu
2019-01-21 7:57 ` [PATCH RFC 13/24] mm: merge parameters for change_protection() Peter Xu
2019-01-21 13:54 ` Jerome Glisse
2019-01-24 5:22 ` Peter Xu
2019-01-21 7:57 ` [PATCH RFC 14/24] userfaultfd: wp: apply _PAGE_UFFD_WP bit Peter Xu
2019-01-21 7:57 ` [PATCH RFC 15/24] mm: export wp_page_copy() Peter Xu
2019-01-21 7:57 ` [PATCH RFC 16/24] userfaultfd: wp: handle COW properly for uffd-wp Peter Xu
2019-01-21 7:57 ` [PATCH RFC 17/24] userfaultfd: wp: drop _PAGE_UFFD_WP properly when fork Peter Xu
2019-01-21 7:57 ` [PATCH RFC 18/24] userfaultfd: wp: add pmd_swp_*uffd_wp() helpers Peter Xu
2019-01-21 7:57 ` [PATCH RFC 19/24] userfaultfd: wp: support swap and page migration Peter Xu
2019-01-21 7:57 ` [PATCH RFC 20/24] userfaultfd: wp: don't wake up when doing write protect Peter Xu
2019-01-21 11:10 ` Mike Rapoport
2019-01-24 5:36 ` Peter Xu
2019-01-21 7:57 ` [PATCH RFC 21/24] khugepaged: skip collapse if uffd-wp detected Peter Xu
2019-01-21 7:57 ` [PATCH RFC 22/24] userfaultfd: wp: UFFDIO_REGISTER_MODE_WP documentation update Peter Xu
2019-01-21 7:57 ` [PATCH RFC 23/24] userfaultfd: selftests: refactor statistics Peter Xu
2019-01-21 7:57 ` [PATCH RFC 24/24] userfaultfd: selftests: add write-protect test Peter Xu
2019-01-21 14:33 ` [PATCH RFC 00/24] userfaultfd: write protection support David Hildenbrand
2019-01-22 3:18 ` Peter Xu
2019-01-22 8:59 ` David Hildenbrand
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