linux-kernel - [PATCH 4.19 45/58] KVM: x86: Mark CR4.TSD as being possibly owned by the guest

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: <20200714184058.398101684@linuxfoundation.org>
Date:   Tue, 14 Jul 2020 20:44:18 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH 4.19 45/58] KVM: x86: Mark CR4.TSD as being possibly owned by the guest

From: Sean Christopherson <sean.j.christopherson@...el.com>

commit 7c83d096aed055a7763a03384f92115363448b71 upstream.

Mark CR4.TSD as being possibly owned by the guest as that is indeed the
case on VMX.  Without TSD being tagged as possibly owned by the guest, a
targeted read of CR4 to get TSD could observe a stale value.  This bug
is benign in the current code base as the sole consumer of TSD is the
emulator (for RDTSC) and the emulator always "reads" the entirety of CR4
when grabbing bits.

Add a build-time assertion in to ensure VMX doesn't hand over more CR4
bits without also updating x86.

Fixes: 52ce3c21aec3 ("x86,kvm,vmx: Don't trap writes to CR4.TSD")
Cc: stable@...r.kernel.org
Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
Message-Id: <20200703040422.31536-2-sean.j.christopherson@...el.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/kvm/kvm_cache_regs.h |    2 +-
 arch/x86/kvm/vmx.c            |    2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

--- a/arch/x86/kvm/kvm_cache_regs.h
+++ b/arch/x86/kvm/kvm_cache_regs.h
@@ -5,7 +5,7 @@
 #define KVM_POSSIBLE_CR0_GUEST_BITS X86_CR0_TS
 #define KVM_POSSIBLE_CR4_GUEST_BITS				  \
 	(X86_CR4_PVI | X86_CR4_DE | X86_CR4_PCE | X86_CR4_OSFXSR  \
-	 | X86_CR4_OSXMMEXCPT | X86_CR4_LA57 | X86_CR4_PGE)
+	 | X86_CR4_OSXMMEXCPT | X86_CR4_LA57 | X86_CR4_PGE | X86_CR4_TSD)
 
 static inline unsigned long kvm_register_read(struct kvm_vcpu *vcpu,
 					      enum kvm_reg reg)
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -6335,6 +6335,8 @@ static void vmx_set_constant_host_state(
 
 static void set_cr4_guest_host_mask(struct vcpu_vmx *vmx)
 {
+	BUILD_BUG_ON(KVM_CR4_GUEST_OWNED_BITS & ~KVM_POSSIBLE_CR4_GUEST_BITS);
+
 	vmx->vcpu.arch.cr4_guest_owned_bits = KVM_CR4_GUEST_OWNED_BITS;
 	if (enable_ept)
 		vmx->vcpu.arch.cr4_guest_owned_bits |= X86_CR4_PGE;