From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
commit 7a22e03b0c02988e91003c505b34d752a51de344 upstream.
Check that the per-cpu cluster mask pointer has been set prior to
clearing a dying cpu's bit. The per-cpu pointer is not set until the
target cpu reaches smp_callin() during CPUHP_BRINGUP_CPU, whereas the
teardown function, x2apic_dead_cpu(), is associated with the earlier
CPUHP_X2APIC_PREPARE. If an error occurs before the cpu is awakened,
e.g. if do_boot_cpu() itself fails, x2apic_dead_cpu() will dereference
the NULL pointer and cause a panic.
smpboot: do_boot_cpu failed(-22) to wakeup CPU#1
BUG: kernel NULL pointer dereference, address: 0000000000000008
RIP: 0010:x2apic_dead_cpu+0x1a/0x30
Call Trace:
cpuhp_invoke_callback+0x9a/0x580
_cpu_up+0x10d/0x140
do_cpu_up+0x69/0xb0
smp_init+0x63/0xa9
kernel_init_freeable+0xd7/0x229
? rest_init+0xa0/0xa0
kernel_init+0xa/0x100
ret_from_fork+0x35/0x40
Fixes: 023a611748fd5 ("x86/apic/x2apic: Simplify cluster management")
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/20191001205019.5789-1-sean.j.christopherson@xxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/apic/x2apic_cluster.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/arch/x86/kernel/apic/x2apic_cluster.c
+++ b/arch/x86/kernel/apic/x2apic_cluster.c
@@ -158,7 +158,8 @@ static int x2apic_dead_cpu(unsigned int
{
struct cluster_mask *cmsk = per_cpu(cluster_masks, dead_cpu);
- cpumask_clear_cpu(dead_cpu, &cmsk->mask);
+ if (cmsk)
+ cpumask_clear_cpu(dead_cpu, &cmsk->mask);
free_cpumask_var(per_cpu(ipi_mask, dead_cpu));
return 0;
}
