[PATCH 5.4 143/147] KVM: x86: Fix off-by-one error in kvm_vcpu_ioctl_x86_setup_mce

[Greg Kroah-Hartman]

From: Jim Mattson <jmatt...@google.com>

commit c4e0e4ab4cf3ec2b3f0b628ead108d677644ebd9 upstream.

Bank_num is a one-based count of banks, not a zero-based index. It
overflows the allocated space only when strictly greater than
KVM_MAX_MCE_BANKS.

Fixes: a9e38c3e01ad ("KVM: x86: Catch potential overrun in MCE setup")
Signed-off-by: Jue Wang <j...@google.com>
Signed-off-by: Jim Mattson <jmatt...@google.com>
Reviewed-by: Peter Shier <psh...@google.com>
Message-Id: <20200511225616.19557-1-jmatt...@google.com>
Reviewed-by: Vitaly Kuznetsov <vkuzn...@redhat.com>
Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 arch/x86/kvm/x86.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3682,7 +3682,7 @@ static int kvm_vcpu_ioctl_x86_setup_mce(
        unsigned bank_num = mcg_cap & 0xff, bank;
 
        r = -EINVAL;
-       if (!bank_num || bank_num >= KVM_MAX_MCE_BANKS)
+       if (!bank_num || bank_num > KVM_MAX_MCE_BANKS)
                goto out;
        if (mcg_cap & ~(kvm_mce_cap_supported | 0xff | 0xff0000))
                goto out;