[PATCH 1/2] x86/acpi: Fix the local APIC id validation in case of 0xff

[Dou Liyang]

In MADT, the 0xff is an invalid local APIC id.

When the kernel uses both the local APIC id and x2apic id, it may
affect x2apic.

Only add validation when the kernel parse the local APIC ids.

Reported-by: Yinghai Lu <yinghai@xxxxxxxxxx>
Signed-off-by: Dou Liyang <douly.fnst@xxxxxxxxxxxxxx>
---
 arch/x86/kernel/acpi/boot.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 32a7d70..d642c95 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -233,6 +233,10 @@ acpi_parse_lapic(struct acpi_subtable_header * header, const unsigned long end)
 
 	acpi_table_print_madt_entry(header);
 
+	/* the 0xff is an invalid local APIC id */
+	if (processor->id == 0xff)
+		return -EINVAL;
+
 	/*
 	 * We need to register disabled CPU as well to permit
 	 * counting disabled CPUs. This allows us to size
-- 
2.5.5