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SubjectRe: [PATCH] x86, kdump: Fix efi=noruntime NULL pointer dereference
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On Thu, 2018-08-09 at 12:21 +0800, Dave Young wrote:
> Hi Mike,
>
> Thanks for the patch!
> On 08/08/18 at 04:03pm, Mike Galbraith wrote:
> > When booting with efi=noruntime, we call efi_runtime_map_copy() while
> > loading the kdump kernel, and trip over a NULL efi.memmap.map. Avoid
> > that and a useless allocation when the only mapping we can use (1:1)
> > is not available.
>
> At first glance, efi_get_runtime_map_size should return 0 in case
> noruntime.

What efi does internally at unmap time is to leave everything except
efi.mmap.map untouched, setting it to NULL and turning off EFI_MEMMAP,
rendering efi.mmap.map accessors useless/unsafe without first checking
EFI_MEMMAP.

-Mike

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