linux-kernel - [PATCH 4.4 190/193] kvm: nVMX: Fix kernel panics induced by illegal INVEPT/INVVPID types

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Date:   Fri, 23 Feb 2018 19:27:03 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jim Mattson <jmattson@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jack Wang <jinpu.wang@...fitbricks.com>
Subject: [PATCH 4.4 190/193] kvm: nVMX: Fix kernel panics induced by illegal INVEPT/INVVPID types

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jim Mattson <jmattson@...gle.com>

commit 85c856b39b479dde410ddd09df1da745343010c9 upstream

Bitwise shifts by amounts greater than or equal to the width of the left
operand are undefined. A malicious guest can exploit this to crash a
32-bit host, due to the BUG_ON(1)'s in handle_{invept,invvpid}.

Signed-off-by: Jim Mattson <jmattson@...gle.com>
Message-Id: <1477496318-17681-1-git-send-email-jmattson@...gle.com>
[Change 1UL to 1, to match the range check on the shift count. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
[jwang: port from linux-4.9 to 4.4 ]
Signed-off-by: Jack Wang <jinpu.wang@...fitbricks.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/x86/kvm/vmx.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -7361,7 +7361,7 @@ static int handle_invept(struct kvm_vcpu
 
 	types = (vmx->nested.nested_vmx_ept_caps >> VMX_EPT_EXTENT_SHIFT) & 6;
 
-	if (!(types & (1UL << type))) {
+	if (type >= 32 || !(types & (1 << type))) {
 		nested_vmx_failValid(vcpu,
 				VMXERR_INVALID_OPERAND_TO_INVEPT_INVVPID);
 		skip_emulated_instruction(vcpu);
@@ -7420,7 +7420,7 @@ static int handle_invvpid(struct kvm_vcp
 
 	types = (vmx->nested.nested_vmx_vpid_caps >> 8) & 0x7;
 
-	if (!(types & (1UL << type))) {
+	if (type >= 32 || !(types & (1 << type))) {
 		nested_vmx_failValid(vcpu,
 			VMXERR_INVALID_OPERAND_TO_INVEPT_INVVPID);
 		skip_emulated_instruction(vcpu);