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.
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