[PATCH AUTOSEL 5.6 074/606] KVM: x86: Fix off-by-one error in kvm_vcpu_ioctl_x86_setup_mce

Sasha Levin
2020-06-08T23:16:30Z

From: Jim Mattson <jmattson@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 <juew@google.com>
Signed-off-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Peter Shier <pshier@google.com>
Message-Id: <20200511225616.19557-1-jmattson@google.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
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 56a21dd7c1a0..7f3371a39ed0 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3739,7 +3739,7 @@ static int kvm_vcpu_ioctl_x86_setup_mce(struct kvm_vcpu *vcpu,
unsigned bank_num = mcg_cap & 0xff, bank;

r = -EINVAL;
- if (!bank_num || 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;
--
2.25.1