Marios Pomonis pomonis@google.com writes:
This fixes Spectre-v1/L1TF vulnerabilities in kvm_hv_msr_get_crash_data() and kvm_hv_msr_set_crash_data(). These functions contain index computations that use the (attacker-controlled) MSR number.
Just to educate myself,
in both cases 'index' is equal to 'msr - HV_X64_MSR_CRASH_P0' where 'msr' is constrained: case HV_X64_MSR_CRASH_P0 ... HV_X64_MSR_CRASH_P4: ....
and moreover, kvm_hv_{get,set}_msr_common() is only being called for a narrow set of MSRs. How can an atacker overcome these limitations?
Fixes: commit e7d9513b60e8 ("kvm/x86: added hyper-v crash msrs into kvm hyperv context")
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
arch/x86/kvm/hyperv.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c index 23ff65504d7e..26408434b9bc 100644 --- a/arch/x86/kvm/hyperv.c +++ b/arch/x86/kvm/hyperv.c @@ -809,11 +809,12 @@ static int kvm_hv_msr_get_crash_data(struct kvm_vcpu *vcpu, u32 index, u64 *pdata) { struct kvm_hv *hv = &vcpu->kvm->arch.hyperv;
- size_t size = ARRAY_SIZE(hv->hv_crash_param);
- if (WARN_ON_ONCE(index >= ARRAY_SIZE(hv->hv_crash_param)))
- if (WARN_ON_ONCE(index >= size)) return -EINVAL;
- *pdata = hv->hv_crash_param[index];
- *pdata = hv->hv_crash_param[array_index_nospec(index, size)]; return 0;
} @@ -852,11 +853,12 @@ static int kvm_hv_msr_set_crash_data(struct kvm_vcpu *vcpu, u32 index, u64 data) { struct kvm_hv *hv = &vcpu->kvm->arch.hyperv;
- size_t size = ARRAY_SIZE(hv->hv_crash_param);
- if (WARN_ON_ONCE(index >= ARRAY_SIZE(hv->hv_crash_param)))
- if (WARN_ON_ONCE(index >= size)) return -EINVAL;
- hv->hv_crash_param[index] = data;
- hv->hv_crash_param[array_index_nospec(index, size)] = data; return 0;
}