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Commit f6175f5b authored by Tomoki Sekiyama's avatar Tomoki Sekiyama Committed by Ingo Molnar
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x86/ioapic: Fix NULL pointer dereference on CPU hotplug after disabling irqs 



In current Linux, percpu variable `vector_irq' is not cleared on
offlined cpus while disabling devices' irqs. If the cpu that has
the disabled irqs in vector_irq is hotplugged,
__setup_vector_irq() hits invalid irq vector and may crash.

This bug can be reproduced as following;

  # echo 0 > /sys/devices/system/cpu/cpu7/online
  # modprobe -r some_driver_using_interrupts      # vector_irq@cpu7 uncleared
  # echo 1 > /sys/devices/system/cpu/cpu7/online  # kernel may crash

This patch fixes this bug by clearing vector_irq in
__clear_irq_vector() even if the cpu is offlined.

Signed-off-by: default avatarTomoki Sekiyama <tomoki.sekiyama.qu@hitachi.com>
Acked-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: yrl.pp-manager.tt@hitachi.com
Cc: ltc-kernel@ml.yrl.intra.hitachi.co.jp
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Alexander Gordeev <agordeev@redhat.com>
Link: http://lkml.kernel.org/r/4FC340BE.7080101@hitachi.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 55c844a4

arch/x86/kernel/apic/io_apic.c

+2 −2
Original line number Diff line number Diff line
@@ -1195,7 +1195,7 @@ static void __clear_irq_vector(int irq, struct irq_cfg *cfg) 
	BUG_ON(!cfg->vector);



	vector = cfg->vector;

	for_each_cpu_and(cpu, cfg->domain, cpu_online_mask)

	for_each_cpu(cpu, cfg->domain)

		per_cpu(vector_irq, cpu)[vector] = -1;



	cfg->vector = 0;
@@ -1203,7 +1203,7 @@ static void __clear_irq_vector(int irq, struct irq_cfg *cfg) 


	if (likely(!cfg->move_in_progress))

		return;

	for_each_cpu_and(cpu, cfg->old_domain, cpu_online_mask) {

	for_each_cpu(cpu, cfg->old_domain) {

		for (vector = FIRST_EXTERNAL_VECTOR; vector < NR_VECTORS;

								vector++) {

			if (per_cpu(vector_irq, cpu)[vector] != irq)