linux-kernel - [PATCH 5.17 112/140] KVM: VMX: Exit to userspace if vCPU has injected exception and invalid state

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Date:   Tue, 10 May 2022 15:08:22 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        syzbot+cfafed3bb76d3e37581b@...kaller.appspotmail.com,
        Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.17 112/140] KVM: VMX: Exit to userspace if vCPU has injected exception and invalid state

From: Sean Christopherson <seanjc@...gle.com>

[ Upstream commit 053d2290c0307e3642e75e0185ddadf084dc36c1 ]

Exit to userspace with an emulation error if KVM encounters an injected
exception with invalid guest state, in addition to the existing check of
bailing if there's a pending exception (KVM doesn't support emulating
exceptions except when emulating real mode via vm86).

In theory, KVM should never get to such a situation as KVM is supposed to
exit to userspace before injecting an exception with invalid guest state.
But in practice, userspace can intervene and manually inject an exception
and/or stuff registers to force invalid guest state while a previously
injected exception is awaiting reinjection.

Fixes: fc4fad79fc3d ("KVM: VMX: Reject KVM_RUN if emulation is required with pending exception")
Reported-by: syzbot+cfafed3bb76d3e37581b@...kaller.appspotmail.com
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
Message-Id: <20220502221850.131873-1-seanjc@...gle.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/x86/kvm/vmx/vmx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index ef63cfd57029..267d6dc4b818 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -5473,7 +5473,7 @@ static bool vmx_emulation_required_with_pending_exception(struct kvm_vcpu *vcpu)
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 
 	return vmx->emulation_required && !vmx->rmode.vm86_active &&
-	       vcpu->arch.exception.pending;
+	       (vcpu->arch.exception.pending || vcpu->arch.exception.injected);
 }
 
 static int handle_invalid_guest_state(struct kvm_vcpu *vcpu)
-- 
2.35.1