1 files changed, 60 insertions, 15 deletions

diff --git a/kernel/signal.c b/kernel/signal.c
index 6f3476dc7873..dfcee3888b00 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1298,6 +1298,12 @@ int do_send_sig_info(int sig, struct kernel_siginfo *info, struct task_struct *p
 	return ret;
 }
 
+enum sig_handler {
+	HANDLER_CURRENT, /* If reachable use the current handler */
+	HANDLER_SIG_DFL, /* Always use SIG_DFL handler semantics */
+	HANDLER_EXIT,	 /* Only visible as the process exit code */
+};
+
 /*
  * Force a signal that the process can't ignore: if necessary
  * we unblock the signal and change any SIG_IGN to SIG_DFL.
@@ -1310,7 +1316,8 @@ int do_send_sig_info(int sig, struct kernel_siginfo *info, struct task_struct *p
  * that is why we also clear SIGNAL_UNKILLABLE.
  */
 static int
-force_sig_info_to_task(struct kernel_siginfo *info, struct task_struct *t, bool sigdfl)
+force_sig_info_to_task(struct kernel_siginfo *info, struct task_struct *t,
+	enum sig_handler handler)
 {
 	unsigned long int flags;
 	int ret, blocked, ignored;
@@ -1321,8 +1328,10 @@ force_sig_info_to_task(struct kernel_siginfo *info, struct task_struct *t, bool
 	action = &t->sighand->action[sig-1];
 	ignored = action->sa.sa_handler == SIG_IGN;
 	blocked = sigismember(&t->blocked, sig);
-	if (blocked || ignored || sigdfl) {
+	if (blocked || ignored || (handler != HANDLER_CURRENT)) {
 		action->sa.sa_handler = SIG_DFL;
+		if (handler == HANDLER_EXIT)
+			action->sa.sa_flags |= SA_IMMUTABLE;
 		if (blocked) {
 			sigdelset(&t->blocked, sig);
 			recalc_sigpending_and_wake(t);
@@ -1342,7 +1351,7 @@ force_sig_info_to_task(struct kernel_siginfo *info, struct task_struct *t, bool
 
 int force_sig_info(struct kernel_siginfo *info)
 {
-	return force_sig_info_to_task(info, current, false);
+	return force_sig_info_to_task(info, current, HANDLER_CURRENT);
 }
 
 /*
@@ -1649,6 +1658,32 @@ void force_sig(int sig)
 }
 EXPORT_SYMBOL(force_sig);
 
+void force_fatal_sig(int sig)
+{
+	struct kernel_siginfo info;
+
+	clear_siginfo(&info);
+	info.si_signo = sig;
+	info.si_errno = 0;
+	info.si_code = SI_KERNEL;
+	info.si_pid = 0;
+	info.si_uid = 0;
+	force_sig_info_to_task(&info, current, HANDLER_SIG_DFL);
+}
+
+void force_exit_sig(int sig)
+{
+	struct kernel_siginfo info;
+
+	clear_siginfo(&info);
+	info.si_signo = sig;
+	info.si_errno = 0;
+	info.si_code = SI_KERNEL;
+	info.si_pid = 0;
+	info.si_uid = 0;
+	force_sig_info_to_task(&info, current, HANDLER_EXIT);
+}
+
 /*
  * When things go south during signal handling, we
  * will force a SIGSEGV. And if the signal that caused
@@ -1657,15 +1692,10 @@ EXPORT_SYMBOL(force_sig);
  */
 void force_sigsegv(int sig)
 {
-	struct task_struct *p = current;
-
-	if (sig == SIGSEGV) {
-		unsigned long flags;
-		spin_lock_irqsave(&p->sighand->siglock, flags);
-		p->sighand->action[sig - 1].sa.sa_handler = SIG_DFL;
-		spin_unlock_irqrestore(&p->sighand->siglock, flags);
-	}
-	force_sig(SIGSEGV);
+	if (sig == SIGSEGV)
+		force_fatal_sig(SIGSEGV);
+	else
+		force_sig(SIGSEGV);
 }
 
 int force_sig_fault_to_task(int sig, int code, void __user *addr
@@ -1684,7 +1714,7 @@ int force_sig_fault_to_task(int sig, int code, void __user *addr
 	info.si_flags = flags;
 	info.si_isr = isr;
 #endif
-	return force_sig_info_to_task(&info, t, false);
+	return force_sig_info_to_task(&info, t, HANDLER_CURRENT);
 }
 
 int force_sig_fault(int sig, int code, void __user *addr
@@ -1804,7 +1834,8 @@ int force_sig_seccomp(int syscall, int reason, bool force_coredump)
 	info.si_errno = reason;
 	info.si_arch = syscall_get_arch(current);
 	info.si_syscall = syscall;
-	return force_sig_info_to_task(&info, current, force_coredump);
+	return force_sig_info_to_task(&info, current,
+		force_coredump ? HANDLER_EXIT : HANDLER_CURRENT);
 }
 
 /* For the crazy architectures that include trap information in
@@ -2704,7 +2735,8 @@ relock:
 		if (!signr)
 			break; /* will return 0 */
 
-		if (unlikely(current->ptrace) && signr != SIGKILL) {
+		if (unlikely(current->ptrace) && (signr != SIGKILL) &&
+		    !(sighand->action[signr -1].sa.sa_flags & SA_IMMUTABLE)) {
 			signr = ptrace_signal(signr, &ksig->info);
 			if (!signr)
 				continue;
@@ -4054,6 +4086,10 @@ int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
 	k = &p->sighand->action[sig-1];
 
 	spin_lock_irq(&p->sighand->siglock);
+	if (k->sa.sa_flags & SA_IMMUTABLE) {
+		spin_unlock_irq(&p->sighand->siglock);
+		return -EINVAL;
+	}
 	if (oact)
 		*oact = *k;
 
@@ -4149,6 +4185,15 @@ do_sigaltstack (const stack_t *ss, stack_t *oss, unsigned long sp,
 				ss_mode != 0))
 			return -EINVAL;
 
+		/*
+		 * Return before taking any locks if no actual
+		 * sigaltstack changes were requested.
+		 */
+		if (t->sas_ss_sp == (unsigned long)ss_sp &&
+		    t->sas_ss_size == ss_size &&
+		    t->sas_ss_flags == ss_flags)
+			return 0;
+
 		sigaltstack_lock();
 		if (ss_mode == SS_DISABLE) {
 			ss_size = 0;