linux-kernel - [PATCH v2 06/32] KVM: SVM: Kill the VM instead of the host if MSR interception is buggy

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250610225737.156318-7-seanjc@google.com>
Date: Tue, 10 Jun 2025 15:57:11 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Chao Gao <chao.gao@...el.com>, Borislav Petkov <bp@...en8.de>, Xin Li <xin@...or.com>, 
	Dapeng Mi <dapeng1.mi@...ux.intel.com>, Francesco Lavra <francescolavra.fl@...il.com>, 
	Manali Shukla <Manali.Shukla@....com>
Subject: [PATCH v2 06/32] KVM: SVM: Kill the VM instead of the host if MSR
 interception is buggy

WARN and kill the VM instead of panicking the host if KVM attempts to set
or query MSR interception for an unsupported MSR.  Accessing the MSR
interception bitmaps only meaningfully affects post-VMRUN behavior, and
KVM_BUG_ON() is guaranteed to prevent the current vCPU from doing VMRUN,
i.e. there is no need to panic the entire host.

Opportunistically move the sanity checks about their use to index into the
MSRPM, e.g. so that bugs only WARN and terminate the VM, as opposed to
doing that _and_ generating an out-of-bounds load.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/svm/svm.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index c75977ca600b..7e39b9df61f1 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -824,11 +824,12 @@ static bool msr_write_intercepted(struct kvm_vcpu *vcpu, u32 msr)
 				      to_svm(vcpu)->msrpm;
 
 	offset    = svm_msrpm_offset(msr);
+	if (KVM_BUG_ON(offset == MSR_INVALID, vcpu->kvm))
+		return false;
+
 	bit_write = 2 * (msr & 0x0f) + 1;
 	tmp       = msrpm[offset];
 
-	BUG_ON(offset == MSR_INVALID);
-
 	return test_bit(bit_write, &tmp);
 }
 
@@ -854,12 +855,13 @@ static void set_msr_interception_bitmap(struct kvm_vcpu *vcpu, u32 *msrpm,
 		write = 0;
 
 	offset    = svm_msrpm_offset(msr);
+	if (KVM_BUG_ON(offset == MSR_INVALID, vcpu->kvm))
+		return;
+
 	bit_read  = 2 * (msr & 0x0f);
 	bit_write = 2 * (msr & 0x0f) + 1;
 	tmp       = msrpm[offset];
 
-	BUG_ON(offset == MSR_INVALID);
-
 	read  ? clear_bit(bit_read,  &tmp) : set_bit(bit_read,  &tmp);
 	write ? clear_bit(bit_write, &tmp) : set_bit(bit_write, &tmp);
 
-- 
2.50.0.rc0.642.g800a2b2222-goog