1. do_hardwall_trap() checks ->sighand != NULL and then takes ->siglock.
This is unsafe even if the task can't run (I assume it is pinned to
the same CPU), its parent can reap the task and set ->sighand = NULL
right after this check. Even if the compiler dosn't read ->sighand
twice and this memory can't to away __group_send_sig_info() is wrong
after that. Use do_send_sig_info().
2. Send SIGILL to the thread, not to the whole process. Unless it has
the handler or blocked this kills the whole thread-group as before.
IIUC, different threads can be bound to different rect's.
3. Check PF_EXITING instead of ->sighand. A zombie thread can go away
but its ->sighand can be !NULL.
Reported-by: Matt Fleming <matt@console-pimps.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
ceca3c193e