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authorSean Christopherson <sean.j.christopherson@intel.com>2019-10-01 23:50:19 +0300
committerThomas Gleixner <tglx@linutronix.de>2019-10-15 11:57:09 +0300
commit7a22e03b0c02988e91003c505b34d752a51de344 (patch)
tree92b8c226cf69876a17096c02f87412feca98d7e7 /arch/x86/kernel/apic
parente211288b72f15259da86eed6eca680758dbe9e74 (diff)
downloadlinux-7a22e03b0c02988e91003c505b34d752a51de344.tar.xz
x86/apic/x2apic: Fix a NULL pointer deref when handling a dying cpu
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@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20191001205019.5789-1-sean.j.christopherson@intel.com
Diffstat (limited to 'arch/x86/kernel/apic')
-rw-r--r--arch/x86/kernel/apic/x2apic_cluster.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/x86/kernel/apic/x2apic_cluster.c b/arch/x86/kernel/apic/x2apic_cluster.c
index 45e92cba92f5..b0889c48a2ac 100644
--- a/arch/x86/kernel/apic/x2apic_cluster.c
+++ b/arch/x86/kernel/apic/x2apic_cluster.c
@@ -156,7 +156,8 @@ static int x2apic_dead_cpu(unsigned int dead_cpu)
{
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;
}