linux-kernel - [PATCH v2 8/8] KVM: x86: Bug the VM on an out-of-bounds data read

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Message-Id: <20220526210817.3428868-9-seanjc@google.com>
Date:   Thu, 26 May 2022 21:08:17 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Kees Cook <keescook@...omium.org>,
        Robert Dinse <nanook@...imo.com>
Subject: [PATCH v2 8/8] KVM: x86: Bug the VM on an out-of-bounds data read

Bug the VM and terminate emulation if an out-of-bounds read into the
emulator's data cache occurs.  Knowingly contuining on all but guarantees
that KVM will overwrite random kernel data, which is far, far worse than
killing the VM.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/emulate.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 2aa17462a9ac..39ea9138224c 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1373,7 +1373,8 @@ static int read_emulated(struct x86_emulate_ctxt *ctxt,
 	if (mc->pos < mc->end)
 		goto read_cached;
 
-	WARN_ON((mc->end + size) >= sizeof(mc->data));
+	if (KVM_EMULATOR_BUG_ON((mc->end + size) >= sizeof(mc->data), ctxt))
+		return X86EMUL_UNHANDLEABLE;
 
 	rc = ctxt->ops->read_emulated(ctxt, addr, mc->data + mc->end, size,
 				      &ctxt->exception);
-- 
2.36.1.255.ge46751e96f-goog