50 lines
1.7 KiB
Diff
50 lines
1.7 KiB
Diff
From bb0f06280beb6507226627a85076ae349a23fe22 Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= <rkrcmar@redhat.com>
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Date: Mon, 16 May 2016 09:45:35 -0400
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Subject: [PATCH] KVM: MTRR: remove MSR 0x2f8
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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MSR 0x2f8 accessed the 124th Variable Range MTRR ever since MTRR support
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was introduced by 9ba075a664df ("KVM: MTRR support").
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0x2f8 became harmful when 910a6aae4e2e ("KVM: MTRR: exactly define the
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size of variable MTRRs") shrinked the array of VR MTRRs from 256 to 8,
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which made access to index 124 out of bounds. The surrounding code only
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WARNs in this situation, thus the guest gained a limited read/write
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access to struct kvm_arch_vcpu.
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0x2f8 is not a valid VR MTRR MSR, because KVM has/advertises only 16 VR
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MTRR MSRs, 0x200-0x20f. Every VR MTRR is set up using two MSRs, 0x2f8
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was treated as a PHYSBASE and 0x2f9 would be its PHYSMASK, but 0x2f9 was
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not implemented in KVM, therefore 0x2f8 could never do anything useful
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and getting rid of it is safe.
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This fixes CVE-2016-TBD.
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Fixes: 910a6aae4e2e ("KVM: MTRR: exactly define the size of variable MTRRs")
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Cc: stable@vger.kernel.org
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Reported-by: David Matlack <dmatlack@google.com>
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Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
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---
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arch/x86/kvm/mtrr.c | 2 --
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1 file changed, 2 deletions(-)
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diff --git a/arch/x86/kvm/mtrr.c b/arch/x86/kvm/mtrr.c
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index 3f8c732117ec..c146f3c262c3 100644
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--- a/arch/x86/kvm/mtrr.c
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+++ b/arch/x86/kvm/mtrr.c
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@@ -44,8 +44,6 @@ static bool msr_mtrr_valid(unsigned msr)
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case MSR_MTRRdefType:
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case MSR_IA32_CR_PAT:
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return true;
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- case 0x2f8:
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- return true;
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}
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return false;
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}
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--
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2.5.5
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