Commit 3d32e4dbe71374a6780eaf51d719d76f9a9bf22f

Authored by Quentin Casasnovas
Committed by Paolo Bonzini
1 parent 3f6f1480d8

kvm: fix excessive pages un-pinning in kvm_iommu_map error path.

The third parameter of kvm_unpin_pages() when called from
kvm_iommu_map_pages() is wrong, it should be the number of pages to un-pin
and not the page size.

This error was facilitated with an inconsistent API: kvm_pin_pages() takes
a size, but kvn_unpin_pages() takes a number of pages, so fix the problem
by matching the two.

This was introduced by commit 350b8bd ("kvm: iommu: fix the third parameter
of kvm_iommu_put_pages (CVE-2014-3601)"), which fixes the lack of
un-pinning for pages intended to be un-pinned (i.e. memory leak) but
unfortunately potentially aggravated the number of pages we un-pin that
should have stayed pinned. As far as I understand though, the same
practical mitigations apply.

This issue was found during review of Red Hat 6.6 patches to prepare
Ksplice rebootless updates.

Thanks to Vegard for his time on a late Friday evening to help me in
understanding this code.

Fixes: 350b8bd ("kvm: iommu: fix the third parameter of... (CVE-2014-3601)")
Cc: stable@vger.kernel.org
Signed-off-by: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Jamie Iles <jamie.iles@oracle.com>
Reviewed-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Showing 1 changed file with 4 additions and 4 deletions Side-by-side Diff

... ... @@ -43,13 +43,13 @@
43 43 gfn_t base_gfn, unsigned long npages);
44 44  
45 45 static pfn_t kvm_pin_pages(struct kvm_memory_slot *slot, gfn_t gfn,
46   - unsigned long size)
  46 + unsigned long npages)
47 47 {
48 48 gfn_t end_gfn;
49 49 pfn_t pfn;
50 50  
51 51 pfn = gfn_to_pfn_memslot(slot, gfn);
52   - end_gfn = gfn + (size >> PAGE_SHIFT);
  52 + end_gfn = gfn + npages;
53 53 gfn += 1;
54 54  
55 55 if (is_error_noslot_pfn(pfn))
... ... @@ -119,7 +119,7 @@
119 119 * Pin all pages we are about to map in memory. This is
120 120 * important because we unmap and unpin in 4kb steps later.
121 121 */
122   - pfn = kvm_pin_pages(slot, gfn, page_size);
  122 + pfn = kvm_pin_pages(slot, gfn, page_size >> PAGE_SHIFT);
123 123 if (is_error_noslot_pfn(pfn)) {
124 124 gfn += 1;
125 125 continue;
... ... @@ -131,7 +131,7 @@
131 131 if (r) {
132 132 printk(KERN_ERR "kvm_iommu_map_address:"
133 133 "iommu failed to map pfn=%llx\n", pfn);
134   - kvm_unpin_pages(kvm, pfn, page_size);
  134 + kvm_unpin_pages(kvm, pfn, page_size >> PAGE_SHIFT);
135 135 goto unmap_pages;
136 136 }
137 137