From: Liam Merwick <liam.merwick@oracle.com>
To: Maxim Levitsky <mlevitsk@redhat.com>, kvm@vger.kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
linux-kernel@vger.kernel.org,
Chenyi Qiang <chenyi.qiang@intel.com>,
Yang Zhong <yang.zhong@intel.com>,
x86@kernel.org, Shuah Khan <shuah@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Colton Lewis <coltonlewis@google.com>,
Borislav Petkov <bp@alien8.de>, Peter Xu <peterx@redhat.com>,
Sean Christopherson <seanjc@google.com>,
Jim Mattson <jmattson@google.com>,
linux-kselftest@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
Wei Wang <wei.w.wang@intel.com>,
David Matlack <dmatlack@google.com>,
stable@vger.kernel.org, Liam Merwick <liam.merwick@oracle.com>
Subject: Re: [PATCH v2 4/9] KVM: x86: forcibly leave nested mode on vCPU reset
Date: Mon, 21 Nov 2022 16:31:55 +0000 [thread overview]
Message-ID: <d908d6f4-bf73-27d0-e062-19eeee874f3b@oracle.com> (raw)
In-Reply-To: <20221103141351.50662-5-mlevitsk@redhat.com>
On 03/11/2022 14:13, Maxim Levitsky wrote:
> 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.
"having" is the wrong word here - maybe "not having in the" -> "not
being in" ?
>
> 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>
Reviewed-by: Liam Merwick <liam.merwick@oracle.com>
> ---
> arch/x86/kvm/x86.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 316ab1d5317f92..3fd900504e683b 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -11694,8 +11694,18 @@ 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;
next prev parent reply other threads:[~2022-11-21 16:32 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-03 14:13 [PATCH v2 0/9] nSVM: Security and correctness fixes Maxim Levitsky
2022-11-03 14:13 ` [PATCH v2 1/9] KVM: x86: nSVM: leave nested mode on vCPU free Maxim Levitsky
2022-11-21 16:30 ` Liam Merwick
2022-11-03 14:13 ` [PATCH v2 2/9] KVM: x86: nSVM: harden svm_free_nested against freeing vmcb02 while still in use Maxim Levitsky
2022-11-21 16:30 ` Liam Merwick
2022-11-03 14:13 ` [PATCH v2 3/9] KVM: x86: add kvm_leave_nested Maxim Levitsky
2022-11-21 16:31 ` Liam Merwick
2022-11-03 14:13 ` [PATCH v2 4/9] KVM: x86: forcibly leave nested mode on vCPU reset Maxim Levitsky
2022-11-21 16:31 ` Liam Merwick [this message]
2022-11-03 14:13 ` [PATCH v2 5/9] KVM: selftests: move idt_entry to header Maxim Levitsky
2022-11-21 16:32 ` Liam Merwick
2022-11-03 14:13 ` [PATCH v2 6/9] kvm: selftests: add svm nested shutdown test Maxim Levitsky
2022-11-03 14:28 ` Maxim Levitsky
2022-11-21 16:33 ` Liam Merwick
2022-11-03 14:13 ` [PATCH v2 7/9] KVM: x86: allow L1 to not intercept triple fault Maxim Levitsky
2022-11-21 16:33 ` Liam Merwick
2022-11-03 14:13 ` [PATCH v2 8/9] KVM: selftests: add svm part to triple_fault_test Maxim Levitsky
2022-11-21 16:34 ` Liam Merwick
2022-11-03 14:13 ` [PATCH v2 9/9] KVM: x86: remove exit_int_info warning in svm_handle_exit Maxim Levitsky
2022-11-06 15:53 ` Liam Merwick
2022-11-09 9:15 ` Maxim Levitsky
2022-11-21 16:34 ` Liam Merwick
2022-11-15 14:55 ` [PATCH v2 0/9] nSVM: Security and correctness fixes Maxim Levitsky
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