BACKPORT: FROMGIT: userfaultfd: fix UFFDIO_CONTINUE ioctl request definition

This ioctl request reads from uffdio_continue structure which justifies
_IOC_READ flag.  See NOTEs in include/uapi/asm-generic/ioctl.h for more
information.

Link: https://lkml.kernel.org/r/20210601143432.1002481-1-glebfm@altlinux.org
Link: https://lkml.kernel.org/r/20210531140146.481553-1-glebfm@altlinux.org


Fixes: f619147104c8 ("userfaultfd: add UFFDIO_CONTINUE ioctl")
Signed-off-by: Gleb Fotengauer-Malinovskiy <glebfm@altlinux.org>
Acked-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Axel Rasmussen <axelrasmussen@google.com>
Cc: Daniel Colascione <dancol@google.com>
Cc: Lokesh Gidra <lokeshgidra@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
(cherry picked from commit 3fe04bff515162ae8192d7eae77b9a92ed1aa945
https: //git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
akpm)
Link: https://lore.kernel.org/patchwork/patch/1439728/



Conflicts: include/uapi/linux/userfaultfd.h
(Manual rebase: removed definition of UFFDIO_WRITEPROTECT as it's not
implementation on this kernel)

Signed-off-by: Lokesh Gidra <lokeshgidra@google.com>
Bug: 187930641
Change-Id: I85d83958a99e5c68e1118b6c189c78108e47be6c