percpu cpus_in_cluster is a pointer with CONFIG_CPUMASK_OFFSTACK, cpu_in_cluster is not alloced memory before x2apic_prepare_cpu is invoked, so cpumask_set_cpu would get a NULL pointer bug: BUG: unable to handle kernel NULL pointer dereference at (null) IP: [<ffffffff8105ac25>] x2apic_cluster_probe+0x35/0x70
Signed-off-by: Huaitong Han <[email protected]> --- arch/x86/kernel/apic/x2apic_cluster.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/apic/x2apic_cluster.c b/arch/x86/kernel/apic/x2apic_cluster.c index 6368fa6..6acb055 100644 --- a/arch/x86/kernel/apic/x2apic_cluster.c +++ b/arch/x86/kernel/apic/x2apic_cluster.c @@ -190,9 +190,10 @@ static int x2apic_cluster_probe(void) 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); + cpumask_set_cpu(cpu, per_cpu(cpus_in_cluster, cpu)); + return 1; } -- 1.8.3.1
