From: Sean Christopherson <seanjc@google.com>
To: Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Hou Wenlong <houwenlong.hwl@antgroup.com>
Subject: [PATCH] KVM: x86: Assert that the emulator doesn't load CS with garbage in !RM
Date: Thu, 16 Feb 2023 12:22:54 -0800 [thread overview]
Message-ID: <20230216202254.671772-1-seanjc@google.com> (raw)
Yell loudly if KVM attempts to load CS outside of Real Mode without an
accompanying control transfer type, i.e. on X86_TRANSFER_NONE. KVM uses
X86_TRANSFER_NONE when emulating IRET and exceptions/interrupts for Real
Mode, but IRET emulation for Protected Mode is non-existent. WARN instead
of trying to pass in a less-wrong type, e.g. X86_TRANSFER_RET, as
emulating IRET goes even beyond emulating FAR RET (which KVM also doesn't
fully support).
Reported-by: Hou Wenlong <houwenlong.hwl@antgroup.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/emulate.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index baf97c56aefa..07e5f473f6fe 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1640,6 +1640,14 @@ static int __load_segment_descriptor(struct x86_emulate_ctxt *ctxt,
goto exception;
break;
case VCPU_SREG_CS:
+ /*
+ * KVM uses "none" when loading CS as part of emulating Real
+ * Mode exceptions and IRET (handled above). In all other
+ * cases, loading CS without a control transfer is a KVM bug.
+ */
+ if (WARN_ON_ONCE(transfer == X86_TRANSFER_NONE))
+ goto exception;
+
if (!(seg_desc.type & 8))
goto exception;
base-commit: 62ef199250cd46fb66fe98267137b7f64e0b41b4
--
2.39.2.637.g21b0678d19-goog
next reply other threads:[~2023-02-16 20:23 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-16 20:22 Sean Christopherson [this message]
2023-03-24 23:38 ` [PATCH] KVM: x86: Assert that the emulator doesn't load CS with garbage in !RM Sean Christopherson
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