The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

Possible dependencies:

ed129ec9057f ("KVM: x86: forcibly leave nested mode on vCPU reset") 0aa1837533e5 ("KVM: x86: Properly reset MMU context at vCPU RESET/INIT") b3646477d458 ("KVM: x86: use static calls to reduce kvm_x86_ops overhead") 15b51dc08a34 ("KVM: x86: Take KVM's SRCU lock only if steal time update is needed") 19979fba9bfa ("KVM: x86: Remove obsolete disabling of page faults in kvm_arch_vcpu_put()") 5719455fbd95 ("KVM: SVM: Do not report support for SMM for an SEV-ES guest") f1c6366e3043 ("KVM: SVM: Add required changes to support intercepts under SEV-ES") f9a4d621761a ("KVM: x86: introduce complete_emulated_msr callback") 8b474427cbee ("KVM: x86: use kvm_complete_insn_gp in emulating RDMSR/WRMSR") 2259c17f0188 ("kvm: x86: Sink cpuid update into vendor-specific set_cr4 functions") fb04a1eddb1a ("KVM: X86: Implement ring-based dirty memory tracking") c21d54f0307f ("KVM: x86: hyper-v: allow KVM_GET_SUPPORTED_HV_CPUID as a system ioctl") ee69c92bac61 ("KVM: x86: Return bool instead of int for CR4 and SREGS validity checks") c2fe3cd4604a ("KVM: x86: Move vendor CR4 validity check to dedicated kvm_x86_ops hook") a447e38a7fad ("KVM: VMX: Drop explicit 'nested' check from vmx_set_cr4()") d3a9e4146a6f ("KVM: VMX: Drop guest CPUID check for VMXE in vmx_set_cr4()") a6a0b05da9f3 ("kvm: x86/mmu: Support dirty logging for the TDP MMU") 1d8dd6b3f12b ("kvm: x86/mmu: Support changed pte notifier in tdp MMU") f8e144971c68 ("kvm: x86/mmu: Add access tracking for tdp_mmu") 063afacd8730 ("kvm: x86/mmu: Support invalidate range MMU notifier for TDP MMU")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From ed129ec9057f89d615ba0c81a4984a90345a1684 Mon Sep 17 00:00:00 2001 From: Maxim Levitsky mlevitsk@redhat.com Date: Thu, 3 Nov 2022 16:13:46 +0200 Subject: [PATCH] KVM: x86: forcibly leave nested mode on vCPU reset

While not obivous, kvm_vcpu_reset() leaves the nested mode by clearing 'vcpu->arch.hflags' but it does so without all the required housekeeping.

On SVM, it is possible to have a vCPU reset while in guest mode because unlike VMX, on SVM, INIT's are not latched in SVM non root mode and in addition to that L1 doesn't have to intercept triple fault, which should also trigger L1's reset if happens in L2 while L1 didn't intercept it.

If one of the above conditions happen, KVM will continue to use vmcb02 while not having in the guest mode.

Later the IA32_EFER will be cleared which will lead to freeing of the nested guest state which will (correctly) free the vmcb02, but since KVM still uses it (incorrectly) this will lead to a use after free and kernel crash.

This issue is assigned CVE-2022-3344

Cc: stable@vger.kernel.org Signed-off-by: Maxim Levitsky mlevitsk@redhat.com Message-Id: 20221103141351.50662-5-mlevitsk@redhat.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index ff5be7189237..597d7f804d72 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -12003,8 +12003,18 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event) WARN_ON_ONCE(!init_event && (old_cr0 || kvm_read_cr3(vcpu) || kvm_read_cr4(vcpu)));

+ /* + * SVM doesn't unconditionally VM-Exit on INIT and SHUTDOWN, thus it's + * possible to INIT the vCPU while L2 is active. Force the vCPU back + * into L1 as EFER.SVME is cleared on INIT (along with all other EFER + * bits), i.e. virtualization is disabled. + */ + if (is_guest_mode(vcpu)) + kvm_leave_nested(vcpu); + kvm_lapic_reset(vcpu, init_event);

+ WARN_ON_ONCE(is_guest_mode(vcpu) || is_smm(vcpu)); vcpu->arch.hflags = 0;

vcpu->arch.smi_pending = 0;