[PATCH 4.4 37/91] KVM: x86: Protect kvm_hv_msr_[get|set]_crash_data() from Spectre-v1/L1TF attacks

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

From: Marios Pomonis <pomonis@xxxxxxxxxx>

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@xxxxxxxxxx>
Signed-off-by: Marios Pomonis <pomonis@xxxxxxxxxx>
Reviewed-by: Andrew Honig <ahonig@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 arch/x86/kvm/hyperv.c |   11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -26,6 +26,7 @@
 #include "hyperv.h"
 
 #include <linux/kvm_host.h>
+#include <linux/nospec.h>
 #include <trace/events/kvm.h>
 
 #include "trace.h"
@@ -53,11 +54,12 @@ static int kvm_hv_msr_get_crash_data(str
 				     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;
 }
 
@@ -96,11 +98,12 @@ static int kvm_hv_msr_set_crash_data(str
 				     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;
 }