x86/ACPI/x2APIC: guard against out of range ACPI or APIC IDs

Other than for the legacy APIC, the x2APIC MADT entries have valid
ranges possibly extending beyond what our internal arrays can handle,
and hence we need to guard ourselves against corrupting memory here.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Keir Fraser <keir@xen.org>

diff --git a/xen/arch/x86/acpi/boot.c b/xen/arch/x86/acpi/boot.c
index 0e1d570c29eed03cd714f005474fdd334c2b6bcb..df264233cd2995a784e6b9dc917f3268010b4511 100644 (file)
--- a/xen/arch/x86/acpi/boot.c
+++ b/xen/arch/x86/acpi/boot.c
@@ -97,7 +97,20 @@ acpi_parse_x2apic(struct acpi_subtable_header *header, const unsigned long end)
 
        acpi_table_print_madt_entry(header);
 
-       /* Record local apic id only when enabled */
+       /* Record local apic id only when enabled and fitting. */
+       if (processor->local_apic_id >= MAX_APICS ||
+           processor->uid >= MAX_MADT_ENTRIES) {
+               printk("%sAPIC ID %#x and/or ACPI ID %#x beyond limit"
+                      " - processor ignored\n",
+                      processor->lapic_flags & ACPI_MADT_ENABLED ?
+                               KERN_WARNING "WARNING: " : KERN_INFO,
+                      processor->local_apic_id, processor->uid);
+               /*
+                * Must not return an error here, to prevent
+                * acpi_table_parse_entries() from terminating early.
+                */
+               return 0 /* -ENOSPC */;
+       }
        if (processor->lapic_flags & ACPI_MADT_ENABLED) {
                x86_acpiid_to_apicid[processor->uid] =
                        processor->local_apic_id;