Xen devel - Oct 2013 - [PATCH] 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>

--- a/xen/arch/x86/acpi/boot.c
+++ b/xen/arch/x86/acpi/boot.c
@@ -97,7 +97,20 @@ acpi_parse_x2apic(struct acpi_subtable_h
 
 	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;





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On 30/10/2013 14:28, "Jan Beulich" <JBeulich@suse.com> wrote:
> 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>
> --- a/xen/arch/x86/acpi/boot.c
> +++ b/xen/arch/x86/acpi/boot.c
> @@ -97,7 +97,20 @@ acpi_parse_x2apic(struct acpi_subtable_h
>  
> 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;
> 
> 
>