Commit 14819305 authored Apr 06, 2020 by Peter Xu Committed by Linus Torvalds Apr 07, 2020

userfaultfd: wp: declare _UFFDIO_WRITEPROTECT conditionally



Only declare _UFFDIO_WRITEPROTECT if the user specified
UFFDIO_REGISTER_MODE_WP and if all the checks passed.  Then when the user
registers regions with shmem/hugetlbfs we won't expose the new ioctl to
them.  Even with complete anonymous memory range, we'll only expose the
new WP ioctl bit if the register mode has MODE_WP.

Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Denis Plotnikov <dplotnikov@virtuozzo.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Martin Cracauer <cracauer@cons.org>
Cc: Marty McFadden <mcfadden8@llnl.gov>
Cc: Maya Gokhale <gokhale2@llnl.gov>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@fb.com>
Link: http://lkml.kernel.org/r/20200220163112.11409-18-peterx@redhat.com


Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 57e5d4f2

fs/userfaultfd.c

+13 −3

Original line number	Diff line number	Diff line
		@@ -1495,14 +1495,24 @@ out_unlock:
		up_write(&mm->mmap_sem);
		mmput(mm);
		if (!ret) {
		__u64 ioctls_out;

		ioctls_out = basic_ioctls ? UFFD_API_RANGE_IOCTLS_BASIC :
		UFFD_API_RANGE_IOCTLS;

		/*
		* Declare the WP ioctl only if the WP mode is
		* specified and all checks passed with the range
		*/
		if (!(uffdio_register.mode & UFFDIO_REGISTER_MODE_WP))
		ioctls_out &= ~((__u64)1 << _UFFDIO_WRITEPROTECT);

		/*
		* Now that we scanned all vmas we can already tell
		* userland which ioctls methods are guaranteed to
		* succeed on this range.
		*/
		if (put_user(basic_ioctls ? UFFD_API_RANGE_IOCTLS_BASIC :
		UFFD_API_RANGE_IOCTLS,
		&user_uffdio_register->ioctls))
		if (put_user(ioctls_out, &user_uffdio_register->ioctls))
		ret = -EFAULT;
		}
		out:

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