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From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Jim Mattson <jmattson@google.com>,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	Liran Alon <liran.alon@oracle.com>,
	Miaohe Lin <linmiaohe@huawei.com>
Subject: [PATCH 1/6] KVM: nVMX: avoid NULL pointer dereference with incorrect EVMCS GPAs
Date: Mon,  9 Mar 2020 16:52:11 +0100	[thread overview]
Message-ID: <20200309155216.204752-2-vkuznets@redhat.com> (raw)
In-Reply-To: <20200309155216.204752-1-vkuznets@redhat.com>

When an EVMCS enabled L1 guest on KVM will tries doing enlightened VMEnter
with EVMCS GPA = 0 the host crashes because the

evmcs_gpa != vmx->nested.hv_evmcs_vmptr

condition in nested_vmx_handle_enlightened_vmptrld() will evaluate to
false (as nested.hv_evmcs_vmptr is zeroed after init). The crash will
happen on vmx->nested.hv_evmcs pointer dereference.

Another problematic EVMCS ptr value is '-1' but it only causes host crash
after nested_release_evmcs() invocation. The problem is exactly the same as
with '0', we mistakenly think that the EVMCS pointer hasn't changed and
thus nested.hv_evmcs_vmptr is valid.

Resolve the issue by adding an additional !vmx->nested.hv_evmcs
check to nested_vmx_handle_enlightened_vmptrld(), this way we will
always be trying kvm_vcpu_map() when nested.hv_evmcs is NULL
and this is supposed to catch all invalid EVMCS GPAs.

Also, initialize hv_evmcs_vmptr to '0' in nested_release_evmcs()
to be consistent with initialization where we don't currently
set hv_evmcs_vmptr to '-1'.

Cc: stable@vger.kernel.org
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 arch/x86/kvm/vmx/nested.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index e920d7834d73..9750e590c89d 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -224,7 +224,7 @@ static inline void nested_release_evmcs(struct kvm_vcpu *vcpu)
 		return;
 
 	kvm_vcpu_unmap(vcpu, &vmx->nested.hv_evmcs_map, true);
-	vmx->nested.hv_evmcs_vmptr = -1ull;
+	vmx->nested.hv_evmcs_vmptr = 0;
 	vmx->nested.hv_evmcs = NULL;
 }
 
@@ -1923,7 +1923,8 @@ static int nested_vmx_handle_enlightened_vmptrld(struct kvm_vcpu *vcpu,
 	if (!nested_enlightened_vmentry(vcpu, &evmcs_gpa))
 		return 1;
 
-	if (unlikely(evmcs_gpa != vmx->nested.hv_evmcs_vmptr)) {
+	if (unlikely(!vmx->nested.hv_evmcs ||
+		     evmcs_gpa != vmx->nested.hv_evmcs_vmptr)) {
 		if (!vmx->nested.hv_evmcs)
 			vmx->nested.current_vmptr = -1ull;
 
-- 
2.24.1


  reply	other threads:[~2020-03-09 15:52 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-09 15:52 [PATCH 0/6] KVM: nVMX: propperly handle enlightened vmptrld failure conditions Vitaly Kuznetsov
2020-03-09 15:52 ` Vitaly Kuznetsov [this message]
2020-03-09 15:52 ` [PATCH 2/6] KVM: nVMX: stop abusing need_vmcs12_to_shadow_sync for eVMCS mapping Vitaly Kuznetsov
2020-03-09 15:52 ` [PATCH 3/6] KVM: nVMX: properly handle errors in nested_vmx_handle_enlightened_vmptrld() Vitaly Kuznetsov
2020-03-10 20:08   ` kbuild test robot
2020-03-10 20:08   ` [RFC PATCH] KVM: nVMX: nested_vmx_handle_enlightened_vmptrld() can be static kbuild test robot
2020-03-11 11:49     ` Vitaly Kuznetsov
2020-03-11 17:45       ` Paolo Bonzini
2020-03-09 15:52 ` [PATCH 4/6] KVM: selftests: define and use EVMCS_VERSION Vitaly Kuznetsov
2020-03-09 15:52 ` [PATCH 5/6] KVM: selftests: test enlightened vmenter with wrong eVMCS version Vitaly Kuznetsov
2020-03-09 15:52 ` [PATCH 6/6] KVM: selftests: enlightened VMPTRLD with an incorrect GPA Vitaly Kuznetsov
2020-03-14 11:52 ` [PATCH 0/6] KVM: nVMX: propperly handle enlightened vmptrld failure conditions Paolo Bonzini
2020-03-10  2:15 [PATCH 1/6] KVM: nVMX: avoid NULL pointer dereference with incorrect EVMCS GPAs linmiaohe

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