KVM: x86: Protect kvm_hv_msr_[get|set]_crash_data() from Spectre-v1/L1TF attacks

commit 8618793750071d66028584a83ed0b4fa7eb4f607 upstream.

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.

Fixes: 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
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 42b1c83..5e837c9 100644 (file)
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -28,6 +28,7 @@
 
 #include <linux/kvm_host.h>
 #include <linux/highmem.h>
+#include <linux/nospec.h>
 #include <asm/apicdef.h>
 #include <trace/events/kvm.h>
 
@@ -719,11 +720,12 @@ 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;
 }
 
@@ -762,11 +764,12 @@ 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;
 }