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Subject[PATCH 4.4 37/91] KVM: x86: Protect kvm_hv_msr_[get|set]_crash_data() from Spectre-v1/L1TF attacks
Date
From: Marios Pomonis <pomonis@google.com>

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>

---
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;
}


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