[3.5.y.z extended stable] Patch "KVM: MMU: handle invalid root_hpa at __direct_map" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    KVM: MMU: handle invalid root_hpa at __direct_map

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 01e6af8e87eb6f8928f0b7e896b3a45ef828e334 Mon Sep 17 00:00:00 2001
From: Marcelo Tosatti <mtosatti at redhat.com>
Date: Thu, 19 Dec 2013 15:28:51 -0200
Subject: KVM: MMU: handle invalid root_hpa at __direct_map

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 at redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
Cc: Josh Boyer <jwboyer at fedoraproject.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.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