[Xen-changelog] [xen master] x86/mm: fix invalid unlinking of nested p2m tables

[patchbot@xxxxxxx]

commit f0fc1e8294a963528556b0862c06bb3fcf7c390a
Author:     Matthew Daley <mattjd@xxxxxxxxx>
AuthorDate: Thu Feb 28 18:16:04 2013 +1300
Commit:     Tim Deegan <tim@xxxxxxx>
CommitDate: Thu Feb 28 10:56:32 2013 +0000

    x86/mm: fix invalid unlinking of nested p2m tables
    
    Commit 90805dc (c/s 26387:4056e5a3d815) ("EPT: Make ept data stucture or
    operations neutral") makes nested p2m tables be unlinked from the host
    p2m table before their destruction (in p2m_teardown_nestedp2m).
    However, by this time the host p2m table has already been torn down,
    leading to a possible race condition where another allocation between
    the two kinds of table being torn down can lead to a linked list
    assertion with debug=y builds or memory corruption on debug=n ones.
    
    Fix by swapping the order the two kinds of table are torn down in. While
    at it, remove the condition in p2m_final_teardown, as it is already
    checked identically in p2m_teardown_hostp2m itself.
    
    Signed-off-by: Matthew Daley <mattjd@xxxxxxxxx>
    Acked-by: Tim Deegan <tim@xxxxxxx>
---
 xen/arch/x86/mm/p2m.c |    8 +++-----
 1 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index b70716d..4837de3 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -488,15 +488,13 @@ void p2m_teardown(struct p2m_domain *p2m)
 
 void p2m_final_teardown(struct domain *d)
 {
-    /* Iterate over all p2m tables per domain */
-    struct p2m_domain *p2m = p2m_get_hostp2m(d);
-    if ( p2m )
-        p2m_teardown_hostp2m(d);
-
     /* We must teardown unconditionally because
      * we initialise them unconditionally.
      */
     p2m_teardown_nestedp2m(d);
+
+    /* Iterate over all p2m tables per domain */
+    p2m_teardown_hostp2m(d);
 }
 
 
--
generated by git-patchbot for /home/xen/git/xen.git#master

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