Re: [Xen-devel] [PATCH] x86/ACPI/x2APIC: guard against out of range ACPI or APIC IDs

[Keir Fraser <keir.xen@xxxxxxxxx>]

On 30/10/2013 14:28, "Jan Beulich" <JBeulich@xxxxxxxx> 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@xxxxxxxx>

Reviewed-by: Keir Fraser <keir@xxxxxxx>

> --- 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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