[PATCH 04/31] tracehooks: reintroduce tracehook_consider_fatal_signal()

[Oleg Nesterov]

Add the killed tracehook_consider_fatal_signal() back. It has multiple
callers and it is not easy add the necessary checks inline.

Signed-off-by: Oleg Nesterov <oleg at redhat.com>
---
 arch/s390/kernel/traps.c  |    4 ++--
 include/linux/tracehook.h |   22 ++++++++++++++++++++++
 kernel/signal.c           |    4 ++--
 3 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/arch/s390/kernel/traps.c b/arch/s390/kernel/traps.c
index ffabcd9..1018ab6 100644
--- a/arch/s390/kernel/traps.c
+++ b/arch/s390/kernel/traps.c
@@ -329,7 +329,7 @@ void __kprobes do_per_trap(struct pt_regs *regs)
 
 	if (notify_die(DIE_SSTEP, "sstep", regs, 0, 0, SIGTRAP) == NOTIFY_STOP)
 		return;
-	if (!current->ptrace)
+	if (!tracehook_consider_fatal_signal(current, SIGTRAP))
 		return;
 	info.si_signo = SIGTRAP;
 	info.si_errno = 0;
@@ -428,7 +428,7 @@ static void __kprobes illegal_op(struct pt_regs *regs, long pgm_int_code,
 		if (get_user(*((__u16 *) opcode), (__u16 __user *) location))
 			return;
 		if (*((__u16 *) opcode) == S390_BREAKPOINT_U16) {
-			if (current->ptrace) {
+			if (tracehook_consider_fatal_signal(current, SIGTRAP)) {
 				info.si_signo = SIGTRAP;
 				info.si_errno = 0;
 				info.si_code = TRAP_BRKPT;
diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h
index 8cc28bc..ec2af67 100644
--- a/include/linux/tracehook.h
+++ b/include/linux/tracehook.h
@@ -161,6 +161,28 @@ static inline void tracehook_signal_handler(int sig, siginfo_t *info,
 		ptrace_notify(SIGTRAP);
 }
 
+/**
+ * tracehook_consider_fatal_signal - suppress special handling of fatal signal
+ * @task:		task receiving the signal
+ * @sig:		signal number being sent
+ *
+ * Return nonzero to prevent special handling of this termination signal.
+ * Normally handler for signal is %SIG_DFL.  It can be %SIG_IGN if @sig is
+ * ignored, in which case force_sig() is about to reset it to %SIG_DFL.
+ * When this returns zero, this signal might cause a quick termination
+ * that does not give the debugger a chance to intercept the signal.
+ *
+ * Called with or without @task->sighand->siglock held.
+ */
+static inline int tracehook_consider_fatal_signal(struct task_struct *task,
+						  int sig)
+{
+	if (unlikely(task_utrace_flags(task) & (UTRACE_EVENT(SIGNAL_TERM) |
+						UTRACE_EVENT(SIGNAL_CORE))))
+		return 1;
+	return task->ptrace != 0;
+}
+
 #ifdef TIF_NOTIFY_RESUME
 /**
  * set_notify_resume - cause tracehook_notify_resume() to be called
diff --git a/kernel/signal.c b/kernel/signal.c
index 291c970..d7ef0da 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -494,7 +494,7 @@ int unhandled_signal(struct task_struct *tsk, int sig)
 	if (handler != SIG_IGN && handler != SIG_DFL)
 		return 0;
 	/* if ptraced, let the tracer determine */
-	return !tsk->ptrace;
+	return !tracehook_consider_fatal_signal(tsk, sig);
 }
 
 /*
@@ -982,7 +982,7 @@ static void complete_signal(int sig, struct task_struct *p, int group)
 	if (sig_fatal(p, sig) &&
 	    !(signal->flags & (SIGNAL_UNKILLABLE | SIGNAL_GROUP_EXIT)) &&
 	    !sigismember(&t->real_blocked, sig) &&
-	    (sig == SIGKILL || !t->ptrace)) {
+	    (sig == SIGKILL || !tracehook_consider_fatal_signal(t, sig))) {
 		/*
 		 * This signal will be fatal to the whole group.
 		 */
-- 
1.5.5.1