linux-kernel - [tip:irq/urgent] x86/irq: Check for valid irq descriptor in check_irq_vectors_for_cpu

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Date:	Wed, 18 Feb 2015 09:08:24 -0800
From:	tip-bot for Joerg Roedel <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	tglx@...utronix.de, linux@...musvillemoes.dk,
	torvalds@...ux-foundation.org, mingo@...nel.org,
	yinghai@...nel.org, linux-kernel@...r.kernel.org,
	kys@...rosoft.com, jroedel@...e.de, prarit@...hat.com,
	jiang.liu@...ux.intel.com, JBeulich@...e.com, peterz@...radead.org,
	hpa@...or.com
Subject: [tip:irq/urgent] x86/irq:
  Check for valid irq descriptor in check_irq_vectors_for_cpu_disable()

Commit-ID:  d97eb8966c91f2c9d05f0a22eb89ed5b76d966d1
Gitweb:     http://git.kernel.org/tip/d97eb8966c91f2c9d05f0a22eb89ed5b76d966d1
Author:     Joerg Roedel <jroedel@...e.de>
AuthorDate: Wed, 4 Feb 2015 13:33:33 +0100
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Wed, 18 Feb 2015 15:01:42 +0100

x86/irq: Check for valid irq descriptor in check_irq_vectors_for_cpu_disable()

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@...e.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Jiang Liu <jiang.liu@...ux.intel.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Jan Beulich <JBeulich@...e.com>
Cc: K. Y. Srinivasan <kys@...rosoft.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Prarit Bhargava <prarit@...hat.com>
Cc: Rasmus Villemoes <linux@...musvillemoes.dk>
Cc: Yinghai Lu <yinghai@...nel.org>
Cc: alnovak@...e.com
Cc: joro@...tes.org
Link: http://lkml.kernel.org/r/20150204132754.GA10078@suse.de
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 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 705ef8d..67b1cbe 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);
--
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