[Xen-changelog] [xen-unstable] x86: Avoid dereference of 'struct page_info' for invalid MFNs.

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1205921701 0
# Node ID 4af873c95d0b7118ffaea9a4cf96fd92338d144c
# Parent  0901aec1d00b685a0922e916ea9a8e60ea14b8ca
x86: Avoid dereference of 'struct page_info' for invalid MFNs.
Introduced by my changes to Samuel's transitive-privilege patch.
Signed-off-by: Keir Fraser <keir.fraser@xxxxxxxxxx>
---
 xen/arch/x86/mm.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletion(-)

diff -r 0901aec1d00b -r 4af873c95d0b xen/arch/x86/mm.c
--- a/xen/arch/x86/mm.c Wed Mar 19 00:01:25 2008 +0000
+++ b/xen/arch/x86/mm.c Wed Mar 19 10:15:01 2008 +0000
@@ -645,7 +645,7 @@ get_page_from_l1e(
     struct page_info *page = mfn_to_page(mfn);
     uint32_t l1f = l1e_get_flags(l1e);
     struct vcpu *curr = current;
-    struct domain *owner = page_get_owner(page);
+    struct domain *owner;
     int okay;
 
     if ( !(l1f & _PAGE_PRESENT) )
@@ -680,6 +680,7 @@ get_page_from_l1e(
      * until pvfb supports granted mappings. At that time this minor hack
      * can go away.
      */
+    owner = page_get_owner(page);
     if ( unlikely(d != owner) && (owner != NULL) &&
          (d != curr->domain) && IS_PRIV_FOR(d, owner) )
         d = owner;

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