userfaultfd: non-cooperative: robustness check

userfaultfd: non-cooperative: robustness check

Similar to the handle_userfault() case, also make sure to never attempt
to send any event past the PF_EXITING point of no return.

This is purely a robustness check.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Andrea Arcangeli <[email protected]>
Acked-by: Mike Rapoport <[email protected]>
Cc: "Dr. David Alan Gilbert" <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Cc: Hillf Danton <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>