Commit 09fa5296 authored Feb 22, 2017 by Andrea Arcangeli Committed by Linus Torvalds Feb 22, 2017

userfaultfd: non-cooperative: wake userfaults after UFFDIO_UNREGISTER

Userfaults may still happen after the userfaultfd monitor thread
received a UFFD_EVENT_MADVDONTNEED until UFFDIO_UNREGISTER is run.

Wake any pending userfault within UFFDIO_UNREGISTER protected by the
mmap_sem for writing, so they will not be reported to userland leading
to UFFDIO_COPY returning -EINVAL (as the range was already unregistered)
and they will not hang permanently either.

Link: http://lkml.kernel.org/r/20161216144821.5183-16-aarcange@redhat.com


Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Michael Rapoport <RAPOPORT@il.ibm.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 0594f58d

fs/userfaultfd.c

+13 −0

Original line number	Diff line number	Diff line
		@@ -1302,6 +1302,19 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
		start = vma->vm_start;
		vma_end = min(end, vma->vm_end);

		if (userfaultfd_missing(vma)) {
		/*
		* Wake any concurrent pending userfault while
		* we unregister, so they will not hang
		* permanently and it avoids userland to call
		* UFFDIO_WAKE explicitly.
		*/
		struct userfaultfd_wake_range range;
		range.start = start;
		range.len = vma_end - start;
		wake_userfault(vma->vm_userfaultfd_ctx.ctx, &range);
		}

		new_flags = vma->vm_flags & ~(VM_UFFD_MISSING \| VM_UFFD_WP);
		prev = vma_merge(mm, prev, start, vma_end, new_flags,
		vma->anon_vma, vma->vm_file, vma->vm_pgoff,

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