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signal: Restore the stop PTRACE_EVENT_EXIT
commit cf43a75 upstream. In the middle of do_exit() there is there is a call "ptrace_event(PTRACE_EVENT_EXIT, code);" That call places the process in TACKED_TRACED aka "(TASK_WAKEKILL | __TASK_TRACED)" and waits for for the debugger to release the task or SIGKILL to be delivered. Skipping past dequeue_signal when we know a fatal signal has already been delivered resulted in SIGKILL remaining pending and TIF_SIGPENDING remaining set. This in turn caused the scheduler to not sleep in PTACE_EVENT_EXIT as it figured a fatal signal was pending. This also caused ptrace_freeze_traced in ptrace_check_attach to fail because it left a per thread SIGKILL pending which is what fatal_signal_pending tests for. This difference in signal state caused strace to report strace: Exit of unknown pid NNNNN ignored Therefore update the signal handling state like dequeue_signal would when removing a per thread SIGKILL, by removing SIGKILL from the per thread signal mask and clearing TIF_SIGPENDING. Acked-by: Oleg Nesterov <[email protected]> Reported-by: Oleg Nesterov <[email protected]> Reported-by: Ivan Delalande <[email protected]> Cc: [email protected] Fixes: 35634ff ("signal: Always notice exiting tasks") Signed-off-by: "Eric W. Biederman" <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]>
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