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authorMichael S. Tsirkin <mst@redhat.com>2014-08-19 19:14:50 +0800
committerPaolo Bonzini <pbonzini@redhat.com>2014-08-19 15:04:45 +0200
commit350b8bdd689cd2ab2c67c8a86a0be86cfa0751a7 (patch)
tree00f9822472c91756bf1d4c6577972e1d7d582823 /virt/kvm/iommu.c
parent7d1311b93e58ed55f3a31cc8f94c4b8fe988a2b9 (diff)
kvm: iommu: fix the third parameter of kvm_iommu_put_pages (CVE-2014-3601)
The third parameter of kvm_iommu_put_pages is wrong, It should be 'gfn - slot->base_gfn'. By making gfn very large, malicious guest or userspace can cause kvm to go to this error path, and subsequently to pass a huge value as size. Alternatively if gfn is small, then pages would be pinned but never unpinned, causing host memory leak and local DOS. Passing a reasonable but large value could be the most dangerous case, because it would unpin a page that should have stayed pinned, and thus allow the device to DMA into arbitrary memory. However, this cannot happen because of the condition that can trigger the error: - out of memory (where you can't allocate even a single page) should not be possible for the attacker to trigger - when exceeding the iommu's address space, guest pages after gfn will also exceed the iommu's address space, and inside kvm_iommu_put_pages() the iommu_iova_to_phys() will fail. The page thus would not be unpinned at all. Reported-by: Jack Morgenstein <jackm@mellanox.com> Cc: stable@vger.kernel.org Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'virt/kvm/iommu.c')
-rw-r--r--virt/kvm/iommu.c19
1 files changed, 10 insertions, 9 deletions
diff --git a/virt/kvm/iommu.c b/virt/kvm/iommu.c
index 0df7d4b34dfe..714b94932312 100644
--- a/virt/kvm/iommu.c
+++ b/virt/kvm/iommu.c
@@ -61,6 +61,14 @@ static pfn_t kvm_pin_pages(struct kvm_memory_slot *slot, gfn_t gfn,
return pfn;
}
+static void kvm_unpin_pages(struct kvm *kvm, pfn_t pfn, unsigned long npages)
+{
+ unsigned long i;
+
+ for (i = 0; i < npages; ++i)
+ kvm_release_pfn_clean(pfn + i);
+}
+
int kvm_iommu_map_pages(struct kvm *kvm, struct kvm_memory_slot *slot)
{
gfn_t gfn, end_gfn;
@@ -123,6 +131,7 @@ int kvm_iommu_map_pages(struct kvm *kvm, struct kvm_memory_slot *slot)
if (r) {
printk(KERN_ERR "kvm_iommu_map_address:"
"iommu failed to map pfn=%llx\n", pfn);
+ kvm_unpin_pages(kvm, pfn, page_size);
goto unmap_pages;
}
@@ -134,7 +143,7 @@ int kvm_iommu_map_pages(struct kvm *kvm, struct kvm_memory_slot *slot)
return 0;
unmap_pages:
- kvm_iommu_put_pages(kvm, slot->base_gfn, gfn);
+ kvm_iommu_put_pages(kvm, slot->base_gfn, gfn - slot->base_gfn);
return r;
}
@@ -266,14 +275,6 @@ out_unlock:
return r;
}
-static void kvm_unpin_pages(struct kvm *kvm, pfn_t pfn, unsigned long npages)
-{
- unsigned long i;
-
- for (i = 0; i < npages; ++i)
- kvm_release_pfn_clean(pfn + i);
-}
-
static void kvm_iommu_put_pages(struct kvm *kvm,
gfn_t base_gfn, unsigned long npages)
{

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