[PATCH AUTOSEL 3.18 56/98] x86/irq: Check for valid irq descriptor in check_irq_vectors_for_cpu_disable()

[Sasha Levin]

From: Joerg Roedel <jroedel@xxxxxxx>

[ Upstream commit d97eb8966c91f2c9d05f0a22eb89ed5b76d966d1 ]

When an interrupt is migrated away from a cpu it will stay
in its vector_irq array until smp_irq_move_cleanup_interrupt
succeeded. The cfg->move_in_progress flag is cleared already
when the IPI was sent.

When the interrupt is destroyed after migration its 'struct
irq_desc' is freed and the vector_irq arrays are cleaned up.
But since cfg->move_in_progress is already 0 the references
at cpus before the last migration will not be cleared. So
this would leave a reference to an already destroyed irq
alive.

When the cpu is taken down at this point, the
check_irq_vectors_for_cpu_disable() function finds a valid irq
number in the vector_irq array, but gets NULL for its
descriptor and dereferences it, causing a kernel panic.

This has been observed on real systems at shutdown. Add a
check to check_irq_vectors_for_cpu_disable() for a valid
'struct irq_desc' to prevent this issue.

Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Jiang Liu <jiang.liu@xxxxxxxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Jan Beulich <JBeulich@xxxxxxxx>
Cc: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Prarit Bhargava <prarit@xxxxxxxxxx>
Cc: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
Cc: Yinghai Lu <yinghai@xxxxxxxxxx>
Cc: alnovak@xxxxxxxx
Cc: joro@xxxxxxxxxx
Link: http://lkml.kernel.org/r/20150204132754.GA10078@xxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 arch/x86/kernel/irq.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index 37907756fc41..1d6e2946a3da 100644
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -302,6 +302,9 @@ int check_irq_vectors_for_cpu_disable(void)
 		irq = __this_cpu_read(vector_irq[vector]);
 		if (irq >= 0) {
 			desc = irq_to_desc(irq);
+			if (!desc)
+				continue;
+
 			data = irq_desc_get_irq_data(desc);
 			cpumask_copy(&affinity_new, data->affinity);
 			cpu_clear(this_cpu, affinity_new);
-- 
2.17.1