linux-kernel - [PATCH v2] KVM: vmx: add mismatched size assertions in vmcs

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Message-Id: <20210409022456.23528-1-lihaiwei.kernel@gmail.com>
Date:   Fri,  9 Apr 2021 10:24:56 +0800
From:   lihaiwei.kernel@...il.com
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     pbonzini@...hat.com, seanjc@...gle.com, vkuznets@...hat.com,
        wanpengli@...cent.com, jmattson@...gle.com, joro@...tes.org,
        Haiwei Li <lihaiwei@...cent.com>
Subject: [PATCH v2] KVM: vmx: add mismatched size assertions in vmcs_check32()

From: Haiwei Li <lihaiwei@...cent.com>

Add compile-time assertions in vmcs_check32() to disallow accesses to
64-bit and 64-bit high fields via vmcs_{read,write}32().  Upper level KVM
code should never do partial accesses to VMCS fields.  KVM handles the
split accesses automatically in vmcs_{read,write}64() when running as a
32-bit kernel.

Reviewed-and-tested-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Haiwei Li <lihaiwei@...cent.com>
---
v1 -> v2:
* Improve the changelog 

 arch/x86/kvm/vmx/vmx_ops.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/kvm/vmx/vmx_ops.h b/arch/x86/kvm/vmx/vmx_ops.h
index 692b0c3..164b64f 100644
--- a/arch/x86/kvm/vmx/vmx_ops.h
+++ b/arch/x86/kvm/vmx/vmx_ops.h
@@ -37,6 +37,10 @@ static __always_inline void vmcs_check32(unsigned long field)
 {
 	BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6000) == 0,
 			 "32-bit accessor invalid for 16-bit field");
+	BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6001) == 0x2000,
+			 "32-bit accessor invalid for 64-bit field");
+	BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6001) == 0x2001,
+			 "32-bit accessor invalid for 64-bit high field");
 	BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6000) == 0x6000,
 			 "32-bit accessor invalid for natural width field");
 }
-- 
1.8.3.1