[PATCH v2 00/13] KVM: x86: Extend Spectre-v1 mitigation

Marios Pomonis
2019-12-11T20:48:20Z

From: Nick Finco <nifi@google.com>

This extends the Spectre-v1 mitigation introduced in
commit 75f139aaf896 ("KVM: x86: Add memory barrier on vmcs field lookup")
and commit 085331dfc6bb ("x86/kvm: Update spectre-v1 mitigation") in light
of the Spectre-v1/L1TF combination described here:
https://xenbits.xen.org/xsa/advisory-289.html

As reported in the link, an attacker can use the cache-load part of a
Spectre-v1 gadget to bring memory into the L1 cache, then use L1TF to
leak the loaded memory. Note that this attack is not fully mitigated by
core scheduling; firstly when "kvm-intel.vmentry_l1d_flush" is not set
to "always", an attacker could use L1TF on the same thread that loaded the
memory values in the cache on paths that do not flush the L1 cache on
VMEntry. Otherwise, an attacker could perform this attack using a
collusion of two sibling hyperthreads: one that loads memory values in
the cache during VMExit handling and another that performs L1TF to leak
them.

This patch uses array_index_nospec() to prevent index computations from
causing speculative loads into the L1 cache. These cases involve a
bounds check followed by a memory read using the index; this is more
common than the full Spectre-v1 pattern. In some cases, the index
computation can be eliminated entirely by small amounts of refactoring.

Marios Pomonis (13):
KVM: x86: Protect x86_decode_insn from Spectre-v1/L1TF attacks
KVM: x86: Protect kvm_hv_msr_[get|set]_crash_data() from
Spectre-v1/L1TF attacks
KVM: x86: Refactor picdev_write() to prevent Spectre-v1/L1TF attacks
KVM: x86: Protect ioapic_read_indirect() from Spectre-v1/L1TF attacks
KVM: x86: Protect ioapic_write_indirect() from Spectre-v1/L1TF attacks
KVM: x86: Protect kvm_lapic_reg_write() from Spectre-v1/L1TF attacks
KVM: x86: Protect MSR-based index computations in
fixed_msr_to_seg_unit()
KVM: x86: Protect MSR-based index computations in pmu.h
KVM: x86: Protect MSR-based index computations from Spectre-v1/L1TF
attacks in x86.c
KVM: x86: Protect memory accesses from Spectre-v1/L1TF attacks in
x86.c
KVM: x86: Protect exit_reason from being used in Spectre-v1/L1TF
attacks
KVM: x86: Protect DR-based index computations from Spectre-v1/L1TF
attacks
KVM: x86: Protect pmu_intel.c from Spectre-v1/L1TF attacks

arch/x86/kvm/emulate.c | 11 ++++--
arch/x86/kvm/hyperv.c | 10 +++--
arch/x86/kvm/i8259.c | 6 ++-
arch/x86/kvm/ioapic.c | 15 +++++---
arch/x86/kvm/lapic.c | 13 +++++--
arch/x86/kvm/mtrr.c | 8 +++-
arch/x86/kvm/pmu.h | 18 +++++++--
arch/x86/kvm/vmx/pmu_intel.c | 24 ++++++++----
arch/x86/kvm/vmx/vmx.c | 71 +++++++++++++++++++++---------------
arch/x86/kvm/x86.c | 18 +++++++--
10 files changed, 129 insertions(+), 65 deletions(-)

--
2.24.0.393.g34dc348eaf-goog