linux-kernel - [PATCH 4.9 39/39] KVM: nVMX: update last_nonleaf

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Date:   Mon, 16 Oct 2017 18:16:35 +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, Ladi Prosek <lprosek@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH 4.9 39/39] KVM: nVMX: update last_nonleaf_level when initializing nested EPT

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ladi Prosek <lprosek@...hat.com>

commit fd19d3b45164466a4adce7cbff448ba9189e1427 upstream.

The function updates context->root_level but didn't call
update_last_nonleaf_level so the previous and potentially wrong value
was used for page walks.  For example, a zero value of last_nonleaf_level
would allow a potential out-of-bounds access in arch/x86/mmu/paging_tmpl.h's
walk_addr_generic function (CVE-2017-12188).

Fixes: 155a97a3d7c78b46cef6f1a973c831bc5a4f82bb
Signed-off-by: Ladi Prosek <lprosek@...hat.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/kvm/mmu.c |    1 +
 1 file changed, 1 insertion(+)

--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4169,6 +4169,7 @@ void kvm_init_shadow_ept_mmu(struct kvm_
 
 	update_permission_bitmask(vcpu, context, true);
 	update_pkru_bitmask(vcpu, context, true);
+	update_last_nonleaf_level(vcpu, context);
 	reset_rsvds_bits_mask_ept(vcpu, context, execonly);
 	reset_ept_shadow_zero_bits_mask(vcpu, context, execonly);
 }