KVM: x86/mmu: Get root level from walkers when retrieving MMIO SPTE

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Get the so called "root" level from the low level shadow page table
walkers instead of manually attempting to calculate it higher up the
stack, e.g. in get_mmio_spte().  When KVM is using PAE shadow paging,
the starting level of the walk, from the callers perspective, is not
the CR3 root but rather the PDPTR "root".  Checking for reserved bits
from the CR3 root causes get_mmio_spte() to consume uninitialized stack
data due to indexing into sptes[] for a level that was not filled by
get_walk().  This can result in false positives and/or negatives
depending on what garbage happens to be on the stack.

Opportunistically nuke a few extra newlines.

Fixes: 95fb5b0258 ("kvm: x86/mmu: Support MMIO in the TDP MMU")
Reported-by: Richard Herbert <rherbert@sympatico.ca>
Cc: Ben Gardon <bgardon@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20201218003139.2167891-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

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This commit is contained in:

Sean Christopherson 2020-12-17 16:31:37 -08:00 • committed by Paolo Bonzini

parent 2aa078932f

commit 39b4d43e60

3 changed files with 13 additions and 11 deletions

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15

arch/x86/kvm/mmu/mmu.c

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5

arch/x86/kvm/mmu/tdp_mmu.c

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4

arch/x86/kvm/mmu/tdp_mmu.h

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