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Diffstat (limited to 'arch/x86/kvm/lapic.c')
-rw-r--r--arch/x86/kvm/lapic.c20
1 files changed, 18 insertions, 2 deletions
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index e542cf285b51..3c300a196bdf 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -229,6 +229,23 @@ static int kvm_recalculate_phys_map(struct kvm_apic_map *new,
u32 physical_id;
/*
+ * For simplicity, KVM always allocates enough space for all possible
+ * xAPIC IDs. Yell, but don't kill the VM, as KVM can continue on
+ * without the optimized map.
+ */
+ if (WARN_ON_ONCE(xapic_id > new->max_apic_id))
+ return -EINVAL;
+
+ /*
+ * Bail if a vCPU was added and/or enabled its APIC between allocating
+ * the map and doing the actual calculations for the map. Note, KVM
+ * hardcodes the x2APIC ID to vcpu_id, i.e. there's no TOCTOU bug if
+ * the compiler decides to reload x2apic_id after this check.
+ */
+ if (x2apic_id > new->max_apic_id)
+ return -E2BIG;
+
+ /*
* Deliberately truncate the vCPU ID when detecting a mismatched APIC
* ID to avoid false positives if the vCPU ID, i.e. x2APIC ID, is a
* 32-bit value. Any unwanted aliasing due to truncation results will
@@ -253,8 +270,7 @@ static int kvm_recalculate_phys_map(struct kvm_apic_map *new,
*/
if (vcpu->kvm->arch.x2apic_format) {
/* See also kvm_apic_match_physical_addr(). */
- if ((apic_x2apic_mode(apic) || x2apic_id > 0xff) &&
- x2apic_id <= new->max_apic_id)
+ if (apic_x2apic_mode(apic) || x2apic_id > 0xff)
new->phys_map[x2apic_id] = apic;
if (!apic_x2apic_mode(apic) && !new->phys_map[xapic_id])