linux-kernel - [PATCH 4.18 026/158] KVM: VMX: Do not allow reexecute

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Message-Id: <20180917211712.185544286@linuxfoundation.org>
Date:   Tue, 18 Sep 2018 00:40:56 +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, Vitaly Kuznetsov <vkuznets@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Radim Krčmář <rkrcmar@...hat.com>
Subject: [PATCH 4.18 026/158] KVM: VMX: Do not allow reexecute_instruction() when skipping MMIO instr

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

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

From: Sean Christopherson <sean.j.christopherson@...el.com>

commit c4409905cd6eb42cfd06126e9226b0150e05a715 upstream.

Re-execution after an emulation decode failure is only intended to
handle a case where two or vCPUs race to write a shadowed page, i.e.
we should never re-execute an instruction as part of MMIO emulation.
As handle_ept_misconfig() is only used for MMIO emulation, it should
pass EMULTYPE_NO_REEXECUTE when using the emulator to skip an instr
in the fast-MMIO case where VM_EXIT_INSTRUCTION_LEN is invalid.

And because the cr2 value passed to x86_emulate_instruction() is only
destined for use when retrying or reexecuting, we can simply call
emulate_instruction().

Fixes: d391f1207067 ("x86/kvm/vmx: do not use vm-exit instruction length
                      for fast MMIO when running nested")
Cc: Vitaly Kuznetsov <vkuznets@...hat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
Cc: stable@...r.kernel.org
Signed-off-by: Radim Krčmář <rkrcmar@...hat.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
@@ -7539,8 +7539,8 @@ static int handle_ept_misconfig(struct k
 		if (!static_cpu_has(X86_FEATURE_HYPERVISOR))
 			return kvm_skip_emulated_instruction(vcpu);
 		else
-			return x86_emulate_instruction(vcpu, gpa, EMULTYPE_SKIP,
-						       NULL, 0) == EMULATE_DONE;
+			return emulate_instruction(vcpu, EMULTYPE_SKIP) ==
+								EMULATE_DONE;
 	}
 
 	return kvm_mmu_page_fault(vcpu, gpa, PFERR_RSVD_MASK, NULL, 0);