Re: [PATCH AUTOSEL 4.19 17/49] efi/x86/Add missing error handling to old_memmap 1:1 mapping code

[Sasha Levin]

On Sun, Jun 09, 2019 at 08:14:29PM +0200, Ard Biesheuvel wrote:
> On Sat, 8 Jun 2019 at 13:43, Sasha Levin <sashal@xxxxxxxxxx> wrote:
> > From: Gen Zhang <blackgod016574@xxxxxxxxx>
> >
> > [ Upstream commit 4e78921ba4dd0aca1cc89168f45039add4183f8e ]
> >
> > The old_memmap flow in efi_call_phys_prolog() performs numerous memory
> > allocations, and either does not check for failure at all, or it does
> > but fails to propagate it back to the caller, which may end up calling
> > into the firmware with an incomplete 1:1 mapping.
> >
> > So let's fix this by returning NULL from efi_call_phys_prolog() on
> > memory allocation failures only, and by handling this condition in the
> > caller. Also, clean up any half baked sets of page tables that we may
> > have created before returning with a NULL return value.
> >
> > Note that any failure at this level will trigger a panic() two levels
> > up, so none of this makes a huge difference, but it is a nice cleanup
> > nonetheless.
> >
> > [ardb: update commit log, add efi_call_phys_epilog() call on error path]
> >
> > Signed-off-by: Gen Zhang <blackgod016574@xxxxxxxxx>
> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> > Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> > Cc: Rob Bradford <robert.bradford@xxxxxxxxx>
> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > Cc: linux-efi@xxxxxxxxxxxxxxx
> > Link: http://lkml.kernel.org/r/20190525112559.7917-2-ard.biesheuvel@xxxxxxxxxx
> > Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
> > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
>
> This was already discussed in the thread that proposed this patch for
> stable: please don't queue this right now, the patches are more likely
> to harm than hurt, and they certainly don't fix a security
> vulnerability, as has been claimed.

I've dropped this, thank you.

--
Thanks,
Sasha