From mboxrd@z Thu Jan  1 00:00:00 1970
From: Matt Fleming <matt-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org>
Subject: Re: [PATCH v2] EFI: make for_each_efi_memory_desc_in_map() cope with
 running on Xen
Date: Tue, 16 Aug 2016 12:49:17 +0100
Message-ID: <20160816114917.GM30909@codeblueprint.co.uk>
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To: Jan Beulich <JBeulich-IBi9RG/b67k@public.gmane.org>
Cc: Vitaly Kuznetsov <vkuznets-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Jiri Slaby <jslaby-AlSwsSmVLrQ@public.gmane.org>, linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Mark Rutland <mark.rutland-5wv7dgnIgG8@public.gmane.org>
List-Id: linux-efi@vger.kernel.org

On Mon, 15 Aug, at 09:05:45AM, Jan Beulich wrote:
> While commit 55f1ea15216 ("efi: Fix for_each_efi_memory_desc_in_map()
> for empty memmaps") made an attempt to deal with empty memory maps, it
> didn't address the case where the desc_size field never gets set, as is
> apparently the case when running under Xen.
> 
> Reported-by: <lists-Ilq5uHa1fWNWk0Htik3J/w@public.gmane.org>
> Cc: Vitaly Kuznetsov <vkuznets-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> Cc: Jiri Slaby <jslaby-AlSwsSmVLrQ@public.gmane.org>
> Signed-off-by: Jan Beulich <jbeulich-IBi9RG/b67k@public.gmane.org>
> Tested-by: <lists-Ilq5uHa1fWNWk0Htik3J/w@public.gmane.org>
> ---
> v2: Add comment.
> ---
>  include/linux/efi.h |    6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> --- 4.8-rc2/include/linux/efi.h
> +++ 4.8-rc2-EFI-memdesc-iterator-Xen/include/linux/efi.h
> @@ -946,7 +946,11 @@ extern int efi_memattr_apply_permissions
>  /* Iterate through an efi_memory_map */
>  #define for_each_efi_memory_desc_in_map(m, md)				   \
>  	for ((md) = (m)->map;						   \
> -	     ((void *)(md) + (m)->desc_size) <= (m)->map_end;		   \
> +	     /*								   \
> +	      * Leverage wrapping of the calculation to avoid an infinite  \
> +	      * loop when all three values are zero.			   \
> +	      */							   \
> +	     ((void *)(md) + (m)->desc_size - 1) < (m)->map_end;	   \
>  	     (md) = (void *)(md) + (m)->desc_size)
>  

Thanks Jan, applied to the 'urgent' EFI queue and tagged for stable.
I'll send it out this week.