From: Alex Williamson <alex.williamson@redhat.com>
Date: Wed, 18 Apr 2012 03:46:44 +0000 (-0600)
Subject: KVM: lock slots_lock around device assignment
X-Git-Tag: v2.6.39-400.9.0~516^2~13
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=bb46421babf101754fa60bd022d0e5e99e2059dd;p=users%2Fjedix%2Flinux-maple.git

KVM: lock slots_lock around device assignment

Bugdb: 13966
As pointed out by Jason Baron, when assigning a device to a guest
we first set the iommu domain pointer, which enables mapping
and unmapping of memory slots to the iommu.  This leaves a window
where this path is enabled, but we haven't synchronized the iommu
mappings to the existing memory slots.  Thus a slot being removed
at that point could send us down unexpected code paths removing
non-existent pinnings and iommu mappings.  Take the slots_lock
around creating the iommu domain and initial mappings as well as
around iommu teardown to avoid this race.

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

This fixes: CVE-2012-2121
Conflicts:

	virt/kvm/iommu.c
---

diff --git a/virt/kvm/iommu.c b/virt/kvm/iommu.c
index d20006dfe988..55ab345dd09a 100644
--- a/virt/kvm/iommu.c
+++ b/virt/kvm/iommu.c
@@ -232,18 +232,18 @@ int kvm_iommu_map_guest(struct kvm *kvm)
 		return -ENODEV;
 	}
 
+
+	mutex_lock(&kvm->slots_lock);
 	kvm->arch.iommu_domain = iommu_domain_alloc();
 	if (!kvm->arch.iommu_domain)
-		return -ENOMEM;
+		goto out_unlock;
 
 	r = kvm_iommu_map_memslots(kvm);
 	if (r)
-		goto out_unmap;
-
-	return 0;
+		kvm_iommu_unmap_memslots(kvm);
 
-out_unmap:
-	kvm_iommu_unmap_memslots(kvm);
+out_unlock:
+	mutex_unlock(&kvm->slots_lock);
 	return r;
 }
 
@@ -320,7 +320,11 @@ int kvm_iommu_unmap_guest(struct kvm *kvm)
 	if (!domain)
 		return 0;
 
+	mutex_lock(&kvm->slots_lock);
 	kvm_iommu_unmap_memslots(kvm);
+	kvm->arch.iommu_domain = NULL;
+	mutex_unlock(&kvm->slots_lock);
+
 	iommu_domain_free(domain);
 	return 0;
 }