Commit 75bd665c authored by Andi Kleen's avatar Andi Kleen Committed by Linus Torvalds

[PATCH] x86_64: Fix fast check in safe_smp_processor_id

The APIC ID returned by hard_smp_processor_id can be beyond
NR_CPUS and then overflow the x86_cpu_to_apic[] array.

Add a check for overflow. If it happens then the slow loop below
will catch.

Bug pointed out by Doug Thompson
Signed-off-by: default avatarAndi Kleen <>
Signed-off-by: default avatarLinus Torvalds <>
parent e42f9437
......@@ -520,13 +520,13 @@ asmlinkage void smp_call_function_interrupt(void)
int safe_smp_processor_id(void)
int apicid, i;
unsigned apicid, i;
if (disable_apic)
return 0;
apicid = hard_smp_processor_id();
if (x86_cpu_to_apicid[apicid] == apicid)
if (apicid < NR_CPUS && x86_cpu_to_apicid[apicid] == apicid)
return apicid;
for (i = 0; i < NR_CPUS; ++i) {
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