linux-kernel - Re: [PATCH v7 1/3] efi/x86: Fix EFI memory map corruption with kexec

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Date: Wed, 5 Jun 2024 09:58:56 +0800
From: Dave Young <dyoung@...hat.com>
To: "Kalra, Ashish" <ashish.kalra@....com>
Cc: Borislav Petkov <bp@...en8.de>, Mike Rapoport <rppt@...nel.org>, tglx@...utronix.de, mingo@...hat.com, 
	dave.hansen@...ux.intel.com, x86@...nel.org, rafael@...nel.org, hpa@...or.com, 
	peterz@...radead.org, adrian.hunter@...el.com, 
	sathyanarayanan.kuppuswamy@...ux.intel.com, jun.nakajima@...el.com, 
	rick.p.edgecombe@...el.com, thomas.lendacky@....com, michael.roth@....com, 
	seanjc@...gle.com, kai.huang@...el.com, bhe@...hat.com, 
	kirill.shutemov@...ux.intel.com, bdas@...hat.com, vkuznets@...hat.com, 
	dionnaglaze@...gle.com, anisinha@...hat.com, jroedel@...e.de, ardb@...nel.org, 
	kexec@...ts.infradead.org, linux-coco@...ts.linux.dev, 
	linux-kernel@...r.kernel.org, dan.j.williams@...el.com
Subject: Re: [PATCH v7 1/3] efi/x86: Fix EFI memory map corruption with kexec

On Wed, 5 Jun 2024 at 09:52, Dave Young <dyoung@...hat.com> wrote:
>
> > >         ...
> > >         if (efi.memmap.flags & (EFI_MEMMAP_MEMBLOCK | EFI_MEMMAP_SLAB)) {
> > >                 __efi_memmap_free(efi.memmap.phys_map,
> > >                                 efi.memmap.desc_size * efi.memmap.nr_map, efi.memmap.flags);
> > >         }
> >
> > From your debugging the memmap should not be freed.  This piece of
> > code was added in below commit,  added Dan Williams in cc list:
> > commit f0ef6523475f18ccd213e22ee593dfd131a2c5ea
> > Author: Dan Williams <dan.j.williams@...el.com>
> > Date:   Mon Jan 13 18:22:44 2020 +0100
> >
> >     efi: Fix efi_memmap_alloc() leaks
> >
> >     With efi_fake_memmap() and efi_arch_mem_reserve() the efi table may be
> >     updated and replaced multiple times. When that happens a previous
> >     dynamically allocated efi memory map can be garbage collected. Use the
> >     new EFI_MEMMAP_{SLAB,MEMBLOCK} flags to detect when a dynamically
> >     allocated memory map is being replaced.
> >
>
> Dan, probably those regions should be freed only for "fake" memmap?

Ashish, can you comment out the __efi_memmap_free see if it works for
you just confirm about the behavior.