From: Andrew Cooper <andrew.cooper3@citrix.com>
Date: Thu, 2 Jun 2016 13:19:00 +0000 (+0100)
Subject: xen/arm: Don't free p2m->root in p2m_teardown() before it has been allocated
X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~1027
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=9ab1bd9ab64799816c8223a5f210b7a767ab4ccc;p=xen.git

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@dornerworks.com>
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Julien Grall <julien.grall@arm.com>
---

diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index 838d004fb5..6a19c57d74 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -1408,7 +1408,8 @@ 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;