[PATCH] KVM: x86: Assertions to check no overrun in MSR lists

[Nadav Amit]

Currently there is no check whether shared MSRs list overrun the allocated size
which can results in bugs. In addition there is no check that vmx->guest_msrs
has sufficient space to accommodate all the VMX msrs.  This patch adds the
assertions.

Signed-off-by: Nadav Amit <namit@xxxxxxxxxxxxxxxxx>
---
 arch/x86/kvm/vmx.c | 2 ++
 arch/x86/kvm/x86.c | 1 +
 2 files changed, 3 insertions(+)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 7534a9f..286a931 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -7585,6 +7585,8 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
 		goto free_vcpu;
 
 	vmx->guest_msrs = kmalloc(PAGE_SIZE, GFP_KERNEL);
+	BUILD_BUG_ON(PAGE_SIZE / sizeof(struct shared_msr_entry) < NR_VMX_MSR);
+
 	err = -ENOMEM;
 	if (!vmx->guest_msrs) {
 		goto uninit_vcpu;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index f750b69..f5cd7876 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -212,6 +212,7 @@ static void shared_msr_update(unsigned slot, u32 msr)
 
 void kvm_define_shared_msr(unsigned slot, u32 msr)
 {
+	BUG_ON(slot >= KVM_NR_SHARED_MSRS);
 	if (slot >= shared_msrs_global.nr)
 		shared_msrs_global.nr = slot + 1;
 	shared_msrs_global.msrs[slot] = msr;
-- 
1.9.1

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