[Xen-changelog] [xen stable-4.6] xen/arm: Don't free p2m->root in p2m_teardown() before it has been allocated

[patchbot@xxxxxxx]

commit f354fb4670132c98112222b433ba34fb8edd46f7
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Thu Jun 2 14:19:00 2016 +0100
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Fri Jun 3 11:30:53 2016 +0100

    xen/arm: Don't free p2m->root in p2m_teardown() before it has been allocated
    
    If p2m_init() didn't complete successfully, (e.g. due to VMID
    exhaustion), p2m_teardown() is called and unconditionally tries to free
    p2m->root before it has been allocated.  free_domheap_pages() doesn't
    tolerate NULL pointers.
    
    This is XSA-181
    
    Reported-by: Aaron Cornelius <Aaron.Cornelius@xxxxxxxxxxxxxxx>
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Julien Grall <julien.grall@xxxxxxx>
---
 xen/arch/arm/p2m.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index a4a08f6..063505c 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -1282,7 +1282,8 @@ void p2m_teardown(struct domain *d)
     while ( (pg = page_list_remove_head(&p2m->pages)) )
         free_domheap_page(pg);
 
-    free_domheap_pages(p2m->root, P2M_ROOT_ORDER);
+    if ( p2m->root )
+        free_domheap_pages(p2m->root, P2M_ROOT_ORDER);
 
     p2m->root = NULL;
 
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.6

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