Re: [Xen-devel] [PATCH] ACPI: fix APEI related table size checking

[Huang Ying <ying.huang@xxxxxxxxx>]

On Tue, 2012-10-16 at 15:46 +0100, Jan Beulich wrote:
> On Huang Ying's machine:
> 
> erst_tab->header_length == sizeof(struct acpi_table_einj)
  ~~~~                                                ~~~~

Typo?

Best Regards,
Huang Ying

> but Yinghai reported that on his machine,
> 
> erst_tab->header_length == sizeof(struct acpi_table_einj) -
> sizeof(struct acpi_table_header)
> 
> To make erst table size checking code works on all systems, both
> testing are treated as PASS.
> 
> Same situation applies to einj_tab->header_length, so corresponding
> table size checking is changed in similar way too.
> 
> Originally-by: Yinghai Lu <yinghai@xxxxxxxxxx>
> Signed-off-by: Huang Ying <ying.huang@xxxxxxxxx>
> 
> - use switch() for better readability
> - add comment explaining why a formally invalid size it also being
>   accepted
> - check erst_tab->header.length before even looking at
>   erst_tab->header_length
> - prefer sizeof(*erst_tab) over sizeof(struct acpi_table_erst)
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> --- a/xen/drivers/acpi/apei/erst.c
> +++ b/xen/drivers/acpi/apei/erst.c
> @@ -715,12 +715,23 @@ int erst_clear(u64 record_id)
>  
>  static int __init erst_check_table(struct acpi_table_erst *erst_tab)
>  {
> -     if (erst_tab->header_length != sizeof(struct acpi_table_erst))
> +     if (erst_tab->header.length < sizeof(*erst_tab))
>               return -EINVAL;
> -     if (erst_tab->header.length < sizeof(struct acpi_table_erst))
> +
> +     switch (erst_tab->header_length) {
> +     case sizeof(*erst_tab) - sizeof(erst_tab->header):
> +     /*
> +      * While invalid per specification, there are (early?) systems
> +      * indicating the full header size here, so accept that value too.
> +      */
> +     case sizeof(*erst_tab):
> +             break;
> +     default:
>               return -EINVAL;
> +     }
> +
>       if (erst_tab->entries !=
> -         (erst_tab->header.length - sizeof(struct acpi_table_erst)) /
> +         (erst_tab->header.length - sizeof(*erst_tab)) /
>           sizeof(struct acpi_erst_entry))
>               return -EINVAL;
>  
> 
> 
> 



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