linux-kernel - [PATCH 1/2] x86/x2apic: fix NULL pointer def during boot

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Message-Id: <1470322560-18333-2-git-send-email-lcapitulino@redhat.com>
Date:	Thu,  4 Aug 2016 10:55:59 -0400
From:	Luiz Capitulino <lcapitulino@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	bigeasy@...utronix.de, tglx@...utronix.de, anna-maria@...utronix.de
Subject: [PATCH 1/2] x86/x2apic: fix NULL pointer def during boot

Commit 6b2c28471, moved the allocation of cpus_in_cluster
to the x2apic_prepare_cpu() callback. However, it forgot
to move the cpumask_set_cpu() call that uses it.

This generates a NULL pointer dereference during boot
in machines with x2apic_mode=true.

Signed-off-by: Luiz Capitulino <lcapitulino@...hat.com>
---
 arch/x86/kernel/apic/x2apic_cluster.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/apic/x2apic_cluster.c b/arch/x86/kernel/apic/x2apic_cluster.c
index 6368fa6..18b1704 100644
--- a/arch/x86/kernel/apic/x2apic_cluster.c
+++ b/arch/x86/kernel/apic/x2apic_cluster.c
@@ -165,6 +165,8 @@ int x2apic_prepare_cpu(unsigned int cpu)
 		return -ENOMEM;
 	}
 
+	cpumask_set_cpu(cpu, per_cpu(cpus_in_cluster, cpu));
+
 	return 0;
 }
 
@@ -185,12 +187,9 @@ int x2apic_dead_cpu(unsigned int this_cpu)
 
 static int x2apic_cluster_probe(void)
 {
-	int cpu = smp_processor_id();
-
 	if (!x2apic_mode)
 		return 0;
 
-	cpumask_set_cpu(cpu, per_cpu(cpus_in_cluster, cpu));
 	cpuhp_setup_state(CPUHP_X2APIC_PREPARE, "X2APIC_PREPARE",
 			  x2apic_prepare_cpu, x2apic_dead_cpu);
 	return 1;
-- 
2.5.5