[PATCH 5.5 229/367] KVM: x86: Protect pmu_intel.c from Spectre-v1/L1TF attacks

Greg Kroah-Hartman
2020-02-10T12:59:44Z

From: Marios Pomonis <pomonis@google.com>

commit 66061740f1a487f4ed54fde75e724709f805da53 upstream.

This fixes Spectre-v1/L1TF vulnerabilities in intel_find_fixed_event()
and intel_rdpmc_ecx_to_pmc().
kvm_rdpmc() (ancestor of intel_find_fixed_event()) and
reprogram_fixed_counter() (ancestor of intel_rdpmc_ecx_to_pmc()) are
exported symbols so KVM should treat them conservatively from a security
perspective.

Fixes: 25462f7f5295 ("KVM: x86/vPMU: Define kvm_pmu_ops to support vPMU function dispatch")

Signed-off-by: Nick Finco <nifi@google.com>
Signed-off-by: Marios Pomonis <pomonis@google.com>
Reviewed-by: Andrew Honig <ahonig@google.com>
Cc: stable@vger.kernel.org
Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/kvm/vmx/pmu_intel.c | 24 ++++++++++++++++--------
1 file changed, 16 insertions(+), 8 deletions(-)

--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -86,10 +86,14 @@ static unsigned intel_find_arch_event(st

static unsigned intel_find_fixed_event(int idx)
{
- if (idx >= ARRAY_SIZE(fixed_pmc_events))
+ u32 event;
+ size_t size = ARRAY_SIZE(fixed_pmc_events);
+
+ if (idx >= size)
return PERF_COUNT_HW_MAX;

- return intel_arch_events[fixed_pmc_events[idx]].event_type;
+ event = fixed_pmc_events[array_index_nospec(idx, size)];
+ return intel_arch_events[event].event_type;
}

/* check if a PMC is enabled by comparing it with globl_ctrl bits. */
@@ -130,16 +134,20 @@ static struct kvm_pmc *intel_rdpmc_ecx_t
struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
bool fixed = idx & (1u << 30);
struct kvm_pmc *counters;
+ unsigned int num_counters;

idx &= ~(3u << 30);
- if (!fixed && idx >= pmu->nr_arch_gp_counters)
- return NULL;
- if (fixed && idx >= pmu->nr_arch_fixed_counters)
+ if (fixed) {
+ counters = pmu->fixed_counters;
+ num_counters = pmu->nr_arch_fixed_counters;
+ } else {
+ counters = pmu->gp_counters;
+ num_counters = pmu->nr_arch_gp_counters;
+ }
+ if (idx >= num_counters)
return NULL;
- counters = fixed ? pmu->fixed_counters : pmu->gp_counters;
*mask &= pmu->counter_bitmask[fixed ? KVM_PMC_FIXED : KVM_PMC_GP];
-
- return &counters[idx];
+ return &counters[array_index_nospec(idx, num_counters)];
}

static bool intel_is_valid_msr(struct kvm_vcpu *vcpu, u32 msr)