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From: Matt Fleming <matt-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org>
To: Jeffrey Hugo <jhugo-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
Cc: Ard Biesheuvel
	<ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>,
	Mark Rutland <mark.rutland-5wv7dgnIgG8@public.gmane.org>,
	"linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
	<linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	Timur Tabi <timur-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>,
	Leif Lindholm
	<leif.lindholm-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
Subject: Re: [RFC PATCH] efi/libstub: Retry ExitBootServices if map key is invalid
Date: Mon, 4 Jul 2016 14:44:23 +0100	[thread overview]
Message-ID: <20160704134423.GO8415@codeblueprint.co.uk> (raw)
In-Reply-To: <1b487d6d-624c-6acb-d9c1-318cd63070d5-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>

On Thu, 30 Jun, at 03:05:12PM, Jeffrey Hugo wrote:
> On 6/30/2016 12:31 PM, Ard Biesheuvel wrote:
> >
> >No, I think x86's implementation is incorrect. efi_get_memory_map()
> >should allocate some slack (i.e., the 8 entries you mentioned), and if
> >the first call to ExitBootServices() fails, we should reuse the memory
> >map buffer, and call GetMemoryMap() directly to repopulate it. Then,
> >we call ExitBootServices() once more, or give up if either call fails.
> >
> >This way, we are 100% compliant with the wording of the spec, and err
> >on the side of caution.
> >
> 
> Ok.  Let me take some time to think upon this approach and develop a working
> prototype.
 
If possible I'd much prefer to see this fixed only once in the
shared part of efi/libstub, so that the code in arch/x86 can be
deleted in favour of your more robust patch.

FYI, commit d3768d885c6c ("x86, efi: retry ExitBootServices() on
failure") illustrates that we have hit this bug in the wild on x86.

  parent reply	other threads:[~2016-07-04 13:44 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-30 15:35 [RFC PATCH] efi/libstub: Retry ExitBootServices if map key is invalid Jeff Hugo
     [not found] ` <1467300933-3991-1-git-send-email-jhugo-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
2016-06-30 16:27   ` Mark Rutland
2016-06-30 16:47     ` Ard Biesheuvel
     [not found]       ` <CAKv+Gu_PLqOVZQC4i3v75M0a-Z9tuE86DSU4v=Vg_pBj-5Y1WQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2016-06-30 17:56         ` Jeffrey Hugo
     [not found]           ` <36dc8c28-e659-7d93-d705-ccc7734fd3d2-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
2016-06-30 18:31             ` Ard Biesheuvel
     [not found]               ` <CAKv+Gu8N3ORp_tg80wxJAgyYbNNPtfw2h-Hxy3DMkDcM6MQbAg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2016-06-30 21:05                 ` Jeffrey Hugo
     [not found]                   ` <1b487d6d-624c-6acb-d9c1-318cd63070d5-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
2016-07-04 13:44                     ` Matt Fleming [this message]
2016-07-01 10:00         ` Mark Rutland

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