From a9e38c3e01ad242fe2a625354cf065c34b01e3aa Mon Sep 17 00:00:00 2001
From: Jan Kiszka <jan.kiszka@siemens.com>
Date: Fri, 23 Oct 2009 09:37:00 +0200
Subject: [PATCH] KVM: x86: Catch potential overrun in MCE setup

We only allocate memory for 32 MCE banks (KVM_MAX_MCE_BANKS) but we
allow user space to fill up to 255 on setup (mcg_cap & 0xff), corrupting
kernel memory. Catch these overflows.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
---
 arch/x86/kvm/x86.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9b9695322f567..8a93fa894ba65 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1692,7 +1692,7 @@ static int kvm_vcpu_ioctl_x86_setup_mce(struct kvm_vcpu *vcpu,
 	unsigned bank_num = mcg_cap & 0xff, bank;
 
 	r = -EINVAL;
-	if (!bank_num)
+	if (!bank_num || bank_num >= KVM_MAX_MCE_BANKS)
 		goto out;
 	if (mcg_cap & ~(KVM_MCE_CAP_SUPPORTED | 0xff | 0xff0000))
 		goto out;
-- 
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