From: Alex Williamson <alex.williamson@redhat.com>
Date: Wed, 11 Apr 2012 15:51:49 +0000 (-0600)
Subject: KVM: unmap pages from the iommu when slots are removed
X-Git-Tag: v2.6.39-400.9.0~516^2~14
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=143b0488a302d43d5caf8bdbff505e5db78778fb;p=users%2Fjedix%2Flinux-maple.git

KVM: unmap pages from the iommu when slots are removed

Bugdb: 13966
We've been adding new mappings, but not destroying old mappings.
This can lead to a page leak as pages are pinned using
get_user_pages, but only unpinned with put_page if they still
exist in the memslots list on vm shutdown.  A memslot that is
destroyed while an iommu domain is enabled for the guest will
therefore result in an elevated page reference count that is
never cleared.

Additionally, without this fix, the iommu is only programmed
with the first translation for a gpa.  This can result in
peer-to-peer errors if a mapping is destroyed and replaced by a
new mapping at the same gpa as the iommu will still be pointing
to the original, pinned memory address.
This fixes: CVE-2012-2121

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
---

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 5040e50098195..43207bc148718 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -558,6 +558,7 @@ void kvm_free_irq_source_id(struct kvm *kvm, int irq_source_id);
 
 #ifdef CONFIG_IOMMU_API
 int kvm_iommu_map_pages(struct kvm *kvm, struct kvm_memory_slot *slot);
+void kvm_iommu_unmap_pages(struct kvm *kvm, struct kvm_memory_slot *slot);
 int kvm_iommu_map_guest(struct kvm *kvm);
 int kvm_iommu_unmap_guest(struct kvm *kvm);
 int kvm_assign_device(struct kvm *kvm,
@@ -571,6 +572,11 @@ static inline int kvm_iommu_map_pages(struct kvm *kvm,
 	return 0;
 }
 
+static inline void kvm_iommu_unmap_pages(struct kvm *kvm,
+					 struct kvm_memory_slot *slot)
+{
+}
+
 static inline int kvm_iommu_map_guest(struct kvm *kvm)
 {
 	return -ENODEV;
diff --git a/virt/kvm/iommu.c b/virt/kvm/iommu.c
index 81450204ef6a7..d20006dfe9886 100644
--- a/virt/kvm/iommu.c
+++ b/virt/kvm/iommu.c
@@ -290,6 +290,11 @@ static void kvm_iommu_put_pages(struct kvm *kvm,
 	}
 }
 
+void kvm_iommu_unmap_pages(struct kvm *kvm, struct kvm_memory_slot *slot)
+{
+	kvm_iommu_put_pages(kvm, slot->base_gfn, slot->npages);
+}
+
 static int kvm_iommu_unmap_memslots(struct kvm *kvm)
 {
 	int idx;
@@ -300,7 +305,7 @@ static int kvm_iommu_unmap_memslots(struct kvm *kvm)
 	slots = kvm_memslots(kvm);
 
 	kvm_for_each_memslot(memslot, slots)
-		kvm_iommu_put_pages(kvm, memslot->base_gfn, memslot->npages);
+		kvm_iommu_unmap_pages(kvm, memslot);
 
 	srcu_read_unlock(&kvm->srcu, idx);
 
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 70be0eebac3cd..f5495772c6c01 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -796,12 +796,13 @@ skip_lpage:
 	if (r)
 		goto out_free;
 
-	/* map the pages in iommu page table */
+	/* map/unmap the pages in iommu page table */
 	if (npages) {
 		r = kvm_iommu_map_pages(kvm, &new);
 		if (r)
 			goto out_free;
-	}
+	} else
+		kvm_iommu_unmap_pages(kvm, &old);
 
 	r = -ENOMEM;
 	slots = kzalloc(sizeof(struct kvm_memslots), GFP_KERNEL);