KVM: VMX: Exit to userspace if vCPU has injected exception and invali…

…d state

[ Upstream commit 053d229 ]

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: fc4fad7 ("KVM: VMX: Reject KVM_RUN if emulation is required with pending exception")
Reported-by: syzbot+cfafed3bb76d3e37581b@syzkaller.appspotmail.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220502221850.131873-1-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

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)