3 files changed, 10 insertions, 3 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 0917b3df12d5..fe970cdca83c 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -561,6 +561,8 @@ struct signal_struct {
 #define SIGNAL_CLD_CONTINUED    0x00000020
 #define SIGNAL_CLD_MASK         (SIGNAL_CLD_STOPPED|SIGNAL_CLD_CONTINUED)
 
+#define SIGNAL_UNKILLABLE       0x00000040 /* for init: ignore fatal signals */
+
 /* If true, all threads except ->group_exit_task have pending SIGKILL */
 static inline int signal_group_exit(const struct signal_struct *sig)
 {
diff --git a/init/main.c b/init/main.c
index 624266b524d4..1f4406477f83 100644
--- a/init/main.c
+++ b/init/main.c
@@ -802,6 +802,8 @@ static int noinline init_post(void)
         (void) sys_dup(0);
         (void) sys_dup(0);
 
+        current->signal->flags |= SIGNAL_UNKILLABLE;
+
         if (ramdisk_execute_command) {
                 run_init_process(ramdisk_execute_command);
                 printk(KERN_WARNING "Failed to execute %s\n",
diff --git a/kernel/signal.c b/kernel/signal.c
index 02ef3548aeb0..646a8765696a 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -728,7 +728,8 @@ static void complete_signal(int sig, struct task_struct *p, int group)
          * Found a killable thread.  If the signal will be fatal,
          * then start taking the whole group down immediately.
          */
-        if (sig_fatal(p, sig) && !(signal->flags & SIGNAL_GROUP_EXIT) &&
+        if (sig_fatal(p, sig) &&
+            !(signal->flags & (SIGNAL_UNKILLABLE | SIGNAL_GROUP_EXIT)) &&
             !sigismember(&t->real_blocked, sig) &&
             (sig == SIGKILL || !(t->ptrace & PT_PTRACED))) {
                 /*
@@ -1615,7 +1616,8 @@ static int do_signal_stop(int signr)
         } else {
                 struct task_struct *t;
 
-                if (!likely(sig->flags & SIGNAL_STOP_DEQUEUED) ||
+                if (unlikely((sig->flags & (SIGNAL_STOP_DEQUEUED | SIGNAL_UNKILLABLE))
+                                         != SIGNAL_STOP_DEQUEUED) ||
                     unlikely(signal_group_exit(sig)))
                         return 0;
                 /*
@@ -1761,7 +1763,8 @@ relock:
                 /*
                  * Global init gets no signals it doesn't want.
                  */
-                if (is_global_init(current))
+                if (unlikely(signal->flags & SIGNAL_UNKILLABLE) &&
+                    !signal_group_exit(signal))
                         continue;
 
                 if (sig_kernel_stop(signr)) {