[PATCH] check return value of cpu_callback

[Akinobu Mita <mita@miraclelinux.com>]

Spawing ksoftirqd, migration, or watchdog, and calling init_timers_cpu() may
fail with small memory. If it happens in initcalls, kernel NULL pointer
dereference happens later. This patch makes crash happen immediately in
such cases. It seems a bit better than getting kernel NULL pointer
dereference later.

CC: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Akinobu Mita <mita@miraclelinux.com>

 kernel/sched.c      |    4 +++-
 kernel/softirq.c    |    4 +++-
 kernel/softlockup.c |    3 ++-
 kernel/timer.c      |    4 +++-
 4 files changed, 11 insertions(+), 4 deletions(-)

Index: work-failmalloc/kernel/softirq.c
===================================================================
--- work-failmalloc.orig/kernel/softirq.c
+++ work-failmalloc/kernel/softirq.c
@@ -612,7 +612,9 @@ static struct notifier_block __cpuinitda
 __init int spawn_ksoftirqd(void)
 {
 	void *cpu = (void *)(long)smp_processor_id();
-	cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
+	int err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
+
+	BUG_ON(err == NOTIFY_BAD);
 	cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
 	register_cpu_notifier(&cpu_nfb);
 	return 0;
Index: work-failmalloc/kernel/softlockup.c
===================================================================
--- work-failmalloc.orig/kernel/softlockup.c
+++ work-failmalloc/kernel/softlockup.c
@@ -149,8 +149,9 @@ static struct notifier_block __cpuinitda
 __init void spawn_softlockup_task(void)
 {
 	void *cpu = (void *)(long)smp_processor_id();
+	int err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
 
-	cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
+	BUG_ON(err == NOTIFY_BAD);
 	cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
 	register_cpu_notifier(&cpu_nfb);
 
Index: work-failmalloc/kernel/sched.c
===================================================================
--- work-failmalloc.orig/kernel/sched.c
+++ work-failmalloc/kernel/sched.c
@@ -5237,9 +5237,11 @@ static struct notifier_block __cpuinitda
 int __init migration_init(void)
 {
 	void *cpu = (void *)(long)smp_processor_id();
+	int err;
 
 	/* Start one for the boot CPU: */
-	migration_call(&migration_notifier, CPU_UP_PREPARE, cpu);
+	err = migration_call(&migration_notifier, CPU_UP_PREPARE, cpu);
+	BUG_ON(err == NOTIFY_BAD);
 	migration_call(&migration_notifier, CPU_ONLINE, cpu);
 	register_cpu_notifier(&migration_notifier);
 
Index: work-failmalloc/kernel/timer.c
===================================================================
--- work-failmalloc.orig/kernel/timer.c
+++ work-failmalloc/kernel/timer.c
@@ -1715,8 +1715,10 @@ static struct notifier_block __cpuinitda
 
 void __init init_timers(void)
 {
-	timer_cpu_notify(&timers_nb, (unsigned long)CPU_UP_PREPARE,
+	int err = timer_cpu_notify(&timers_nb, (unsigned long)CPU_UP_PREPARE,
 				(void *)(long)smp_processor_id());
+
+	BUG_ON(err == NOTIFY_BAD);
 	register_cpu_notifier(&timers_nb);
 	open_softirq(TIMER_SOFTIRQ, run_timer_softirq, NULL);
 }