linux-kernel - [PATCH 3.5 40/62] KVM: MMU: handle invalid root_hpa at __direct

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Message-Id: <1394030226-26652-41-git-send-email-luis.henriques@canonical.com>
Date:	Wed,  5 Mar 2014 14:36:44 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Marcelo Tosatti <mtosatti@...hat.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Josh Boyer <jwboyer@...oraproject.org>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.5 40/62] KVM: MMU: handle invalid root_hpa at __direct_map

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

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

From: Marcelo Tosatti <mtosatti@...hat.com>

commit 989c6b34f6a9480e397b170cc62237e89bf4fdb9 upstream.

It is possible for __direct_map to be called on invalid root_hpa
(-1), two examples:

1) try_async_pf -> can_do_async_pf
    -> vmx_interrupt_allowed -> nested_vmx_vmexit
2) vmx_handle_exit -> vmx_interrupt_allowed -> nested_vmx_vmexit

Then to load_vmcs12_host_state and kvm_mmu_reset_context.

Check for this possibility, let fault exception be regenerated.

BZ: https://bugzilla.redhat.com/show_bug.cgi?id=924916

Signed-off-by: Marcelo Tosatti <mtosatti@...hat.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Cc: Josh Boyer <jwboyer@...oraproject.org>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 arch/x86/kvm/mmu.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 57e168e..d6c365f 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2500,6 +2500,9 @@ static int __direct_map(struct kvm_vcpu *vcpu, gpa_t v, int write,
 	int emulate = 0;
 	gfn_t pseudo_gfn;
 
+	if (!VALID_PAGE(vcpu->arch.mmu.root_hpa))
+		return 0;
+
 	for_each_shadow_entry(vcpu, (u64)gfn << PAGE_SHIFT, iterator) {
 		if (iterator.level == level) {
 			unsigned pte_access = ACC_ALL;
-- 
1.9.0

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