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Date: Mon, 18 Feb 2019 14:44:39 +0100 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Oleg Nesterov <oleg@...hat.com>, Ivan Delalande <colona@...sta.com>, "Eric W. Biederman" <ebiederm@...ssion.com> Subject: [PATCH 3.18 103/108] signal: Restore the stop PTRACE_EVENT_EXIT 3.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric W. Biederman <ebiederm@...ssion.com> commit cf43a757fd49442bc38f76088b70c2299eed2c2f 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 <oleg@...hat.com> Reported-by: Oleg Nesterov <oleg@...hat.com> Reported-by: Ivan Delalande <colona@...sta.com> Cc: stable@...r.kernel.org Fixes: 35634ffa1751 ("signal: Always notice exiting tasks") Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- kernel/signal.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) --- a/kernel/signal.c +++ b/kernel/signal.c @@ -2284,9 +2284,12 @@ relock: } /* Has this task already been marked for death? */ - ksig->info.si_signo = signr = SIGKILL; - if (signal_group_exit(signal)) + if (signal_group_exit(signal)) { + ksig->info.si_signo = signr = SIGKILL; + sigdelset(¤t->pending.signal, SIGKILL); + recalc_sigpending(); goto fatal; + } for (;;) { struct k_sigaction *ka;
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