wait_task_stopped: Check p->exit_state instead of TASK_TRACED (CVE-2007-5500)

wait_task_stopped: Check p->exit_state instead of TASK_TRACED (CVE-2007-5500)

patch a3474224e6a01924be40a8255636ea5522c1023a in mainline

The original meaning of the old test (p->state > TASK_STOPPED) was
"not dead", since it was before TASK_TRACED existed and before the
state/exit_state split.  It was a wrong correction in commit
14bf01bb0599c89fc7f426d20353b76e12555308 to make this test for
TASK_TRACED instead.  It should have been changed when TASK_TRACED
was introducted and again when exit_state was introduced.

Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Adrian Bunk <bunk@kernel.org>