[3.5.y.z extended stable] Patch "KVM: x86: Convert vapic synchronization to _cached functions" has been added to staging queue

Luis Henriques luis.henriques at canonical.com
Tue Dec 17 13:31:49 UTC 2013


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

    KVM: x86: Convert vapic synchronization to _cached functions

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 b0611ab8d40c3639b6a7ccf19fe1fb7782d4f0ce Mon Sep 17 00:00:00 2001
From: Andy Honig <ahonig at google.com>
Date: Wed, 20 Nov 2013 10:23:22 -0800
Subject: KVM: x86: Convert vapic synchronization to _cached functions
 (CVE-2013-6368)

commit fda4e2e85589191b123d31cdc21fd33ee70f50fd upstream.

In kvm_lapic_sync_from_vapic and kvm_lapic_sync_to_vapic there is the
potential to corrupt kernel memory if userspace provides an address that
is at the end of a page.  This patches concerts those functions to use
kvm_write_guest_cached and kvm_read_guest_cached.  It also checks the
vapic_address specified by userspace during ioctl processing and returns
an error to userspace if the address is not a valid GPA.

This is generally not guest triggerable, because the required write is
done by firmware that runs before the guest.  Also, it only affects AMD
processors and oldish Intel that do not have the FlexPriority feature
(unless you disable FlexPriority, of course; then newer processors are
also affected).

Fixes: b93463aa59d6 ('KVM: Accelerated apic support')

Reported-by: Andrew Honig <ahonig at google.com>
Signed-off-by: Andrew Honig <ahonig at google.com>
Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
[ luis: backported to 3.5: based on pbonzini backport for <3.10 ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 arch/x86/kvm/lapic.c | 27 +++++++++++++++------------
 arch/x86/kvm/lapic.h |  4 ++--
 arch/x86/kvm/x86.c   | 33 +--------------------------------
 3 files changed, 18 insertions(+), 46 deletions(-)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 399df2f..94e0d9d 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1287,14 +1287,12 @@ void __kvm_migrate_apic_timer(struct kvm_vcpu *vcpu)
 void kvm_lapic_sync_from_vapic(struct kvm_vcpu *vcpu)
 {
 	u32 data;
-	void *vapic;

 	if (!test_bit(KVM_APIC_CHECK_VAPIC, &vcpu->arch.apic_attention))
 		return;

-	vapic = kmap_atomic(vcpu->arch.apic->vapic_page);
-	data = *(u32 *)(vapic + offset_in_page(vcpu->arch.apic->vapic_addr));
-	kunmap_atomic(vapic);
+	kvm_read_guest_cached(vcpu->kvm, &vcpu->arch.apic->vapic_cache, &data,
+				sizeof(u32));

 	apic_set_tpr(vcpu->arch.apic, data & 0xff);
 }
@@ -1304,7 +1302,6 @@ void kvm_lapic_sync_to_vapic(struct kvm_vcpu *vcpu)
 	u32 data, tpr;
 	int max_irr, max_isr;
 	struct kvm_lapic *apic;
-	void *vapic;

 	if (!test_bit(KVM_APIC_CHECK_VAPIC, &vcpu->arch.apic_attention))
 		return;
@@ -1319,18 +1316,24 @@ void kvm_lapic_sync_to_vapic(struct kvm_vcpu *vcpu)
 		max_isr = 0;
 	data = (tpr & 0xff) | ((max_isr & 0xf0) << 8) | (max_irr << 24);

-	vapic = kmap_atomic(vcpu->arch.apic->vapic_page);
-	*(u32 *)(vapic + offset_in_page(vcpu->arch.apic->vapic_addr)) = data;
-	kunmap_atomic(vapic);
+	kvm_write_guest_cached(vcpu->kvm, &vcpu->arch.apic->vapic_cache, &data,
+				sizeof(u32));
 }

-void kvm_lapic_set_vapic_addr(struct kvm_vcpu *vcpu, gpa_t vapic_addr)
+int kvm_lapic_set_vapic_addr(struct kvm_vcpu *vcpu, gpa_t vapic_addr)
 {
-	vcpu->arch.apic->vapic_addr = vapic_addr;
-	if (vapic_addr)
+	if (vapic_addr) {
+		if (kvm_gfn_to_hva_cache_init(vcpu->kvm,
+					&vcpu->arch.apic->vapic_cache,
+					vapic_addr, sizeof(u32)))
+			return -EINVAL;
 		__set_bit(KVM_APIC_CHECK_VAPIC, &vcpu->arch.apic_attention);
-	else
+	} else {
 		__clear_bit(KVM_APIC_CHECK_VAPIC, &vcpu->arch.apic_attention);
+	}
+
+	vcpu->arch.apic->vapic_addr = vapic_addr;
+	return 0;
 }

 int kvm_x2apic_msr_write(struct kvm_vcpu *vcpu, u32 msr, u64 data)
diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
index 6f4ce25..6aec071 100644
--- a/arch/x86/kvm/lapic.h
+++ b/arch/x86/kvm/lapic.h
@@ -15,7 +15,7 @@ struct kvm_lapic {
 	bool irr_pending;
 	void *regs;
 	gpa_t vapic_addr;
-	struct page *vapic_page;
+	struct gfn_to_hva_cache vapic_cache;
 };
 int kvm_create_lapic(struct kvm_vcpu *vcpu);
 void kvm_free_lapic(struct kvm_vcpu *vcpu);
@@ -46,7 +46,7 @@ int kvm_lapic_find_highest_irr(struct kvm_vcpu *vcpu);
 u64 kvm_get_lapic_tscdeadline_msr(struct kvm_vcpu *vcpu);
 void kvm_set_lapic_tscdeadline_msr(struct kvm_vcpu *vcpu, u64 data);

-void kvm_lapic_set_vapic_addr(struct kvm_vcpu *vcpu, gpa_t vapic_addr);
+int kvm_lapic_set_vapic_addr(struct kvm_vcpu *vcpu, gpa_t vapic_addr);
 void kvm_lapic_sync_from_vapic(struct kvm_vcpu *vcpu);
 void kvm_lapic_sync_to_vapic(struct kvm_vcpu *vcpu);

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 671e5df..494817e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2751,8 +2751,7 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
 		r = -EFAULT;
 		if (copy_from_user(&va, argp, sizeof va))
 			goto out;
-		r = 0;
-		kvm_lapic_set_vapic_addr(vcpu, va.vapic_addr);
+		r = kvm_lapic_set_vapic_addr(vcpu, va.vapic_addr);
 		break;
 	}
 	case KVM_X86_SETUP_MCE: {
@@ -5096,33 +5095,6 @@ static void post_kvm_run_save(struct kvm_vcpu *vcpu)
 			!kvm_event_needs_reinjection(vcpu);
 }

-static void vapic_enter(struct kvm_vcpu *vcpu)
-{
-	struct kvm_lapic *apic = vcpu->arch.apic;
-	struct page *page;
-
-	if (!apic || !apic->vapic_addr)
-		return;
-
-	page = gfn_to_page(vcpu->kvm, apic->vapic_addr >> PAGE_SHIFT);
-
-	vcpu->arch.apic->vapic_page = page;
-}
-
-static void vapic_exit(struct kvm_vcpu *vcpu)
-{
-	struct kvm_lapic *apic = vcpu->arch.apic;
-	int idx;
-
-	if (!apic || !apic->vapic_addr)
-		return;
-
-	idx = srcu_read_lock(&vcpu->kvm->srcu);
-	kvm_release_page_dirty(apic->vapic_page);
-	mark_page_dirty(vcpu->kvm, apic->vapic_addr >> PAGE_SHIFT);
-	srcu_read_unlock(&vcpu->kvm->srcu, idx);
-}
-
 static void update_cr8_intercept(struct kvm_vcpu *vcpu)
 {
 	int max_irr, tpr;
@@ -5408,7 +5380,6 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
 	}

 	vcpu->srcu_idx = srcu_read_lock(&kvm->srcu);
-	vapic_enter(vcpu);

 	r = 1;
 	while (r > 0) {
@@ -5465,8 +5436,6 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)

 	srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx);

-	vapic_exit(vcpu);
-
 	return r;
 }

--
1.8.3.2





More information about the kernel-team mailing list