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[3.16.y-ckt,extended,stable] Patch "kvm: fix excessive pages un-pinning in kvm_iommu_map error path." has been added to staging queue

Message ID 1415619116-9649-1-git-send-email-luis.henriques@canonical.com
State New
Headers show

Commit Message

Luis Henriques Nov. 10, 2014, 11:31 a.m. UTC 
This is a note to let you know that I have just added a patch titled

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

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt1.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

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From 74be68b2abf98e04eb56f151c674421fb1383a91 Mon Sep 17 00:00:00 2001
From: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Date: Fri, 17 Oct 2014 22:55:59 +0200
Subject: kvm: fix excessive pages un-pinning in kvm_iommu_map error path.

commit 3d32e4dbe71374a6780eaf51d719d76f9a9bf22f upstream.

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)")
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>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---
 virt/kvm/iommu.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--
2.1.0
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Patch

diff --git a/virt/kvm/iommu.c b/virt/kvm/iommu.c
index 714b94932312..1f0dc1e5f1f0 100644
--- a/virt/kvm/iommu.c
+++ b/virt/kvm/iommu.c
@@ -43,13 +43,13 @@  static void kvm_iommu_put_pages(struct kvm *kvm,
 				gfn_t base_gfn, unsigned long npages);

 static pfn_t kvm_pin_pages(struct kvm_memory_slot *slot, gfn_t gfn,
-			   unsigned long size)
+			   unsigned long npages)
 {
 	gfn_t end_gfn;
 	pfn_t pfn;

 	pfn     = gfn_to_pfn_memslot(slot, gfn);
-	end_gfn = gfn + (size >> PAGE_SHIFT);
+	end_gfn = gfn + npages;
 	gfn    += 1;

 	if (is_error_noslot_pfn(pfn))
@@ -119,7 +119,7 @@  int kvm_iommu_map_pages(struct kvm *kvm, struct kvm_memory_slot *slot)
 		 * Pin all pages we are about to map in memory. This is
 		 * important because we unmap and unpin in 4kb steps later.
 		 */
-		pfn = kvm_pin_pages(slot, gfn, page_size);
+		pfn = kvm_pin_pages(slot, gfn, page_size >> PAGE_SHIFT);
 		if (is_error_noslot_pfn(pfn)) {
 			gfn += 1;
 			continue;
@@ -131,7 +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);
+			kvm_unpin_pages(kvm, pfn, page_size >> PAGE_SHIFT);
 			goto unmap_pages;
 		}