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From: Like Xu <like.xu.linux@gmail.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Jing Liu <jing2.liu@intel.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Sean Christopherson <seanjc@google.com>,
	Jim Mattson <jmattson@google.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Joerg Roedel <joro@8bytes.org>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] KVM: x86/cpuid: Exclude unpermitted xfeatures for vcpu->arch.guest_supported_xcr0
Date: Sun, 23 Jan 2022 13:50:25 +0800	[thread overview]
Message-ID: <20220123055025.81342-1-likexu@tencent.com> (raw)

From: Like Xu <likexu@tencent.com>

A malicious user space can bypass xstate_get_guest_group_perm() in the
KVM_GET_SUPPORTED_CPUID mechanism and obtain unpermitted xfeatures,
since the validity check of xcr0 depends only on guest_supported_xcr0.

Fixes: 445ecdf79be0 ("kvm: x86: Exclude unpermitted xfeatures at KVM_GET_SUPPORTED_CPUID")
Signed-off-by: Like Xu <likexu@tencent.com>
---
 arch/x86/kvm/cpuid.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 3902c28fb6cb..1bd4d560cbdd 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -266,7 +266,8 @@ static void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
 		vcpu->arch.guest_supported_xcr0 = 0;
 	else
 		vcpu->arch.guest_supported_xcr0 =
-			(best->eax | ((u64)best->edx << 32)) & supported_xcr0;
+			(best->eax | ((u64)best->edx << 32)) &
+			(supported_xcr0 & xstate_get_guest_group_perm());
 
 	/*
 	 * Bits 127:0 of the allowed SECS.ATTRIBUTES (CPUID.0x12.0x1) enumerate
-- 
2.33.1


             reply	other threads:[~2022-01-23  5:50 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-23  5:50 Like Xu [this message]
2022-01-24  7:06 ` [PATCH] KVM: x86/cpuid: Exclude unpermitted xfeatures for vcpu->arch.guest_supported_xcr0 Tian, Kevin
2022-01-24  7:17   ` Like Xu
2022-01-24 16:23     ` Sean Christopherson
2022-01-24 16:29       ` Paolo Bonzini
2022-01-25  1:54         ` Tian, Kevin
2022-01-25  8:27           ` Paolo Bonzini
2022-01-26  1:23             ` Tian, Kevin

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