[Xen-changelog] [xen stable-4.4] x86: (allow to) override LIST_POISON*

[patchbot@xxxxxxx]

commit d2cf20efda62a0ea83c6a9e97fba19100df200d6
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Wed Dec 10 12:22:00 2014 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Dec 10 12:22:00 2014 +0100

    x86: (allow to) override LIST_POISON*
    
    Having these point into space not controlled by the hypervisor provides
    an unnecessary attack surface. Allow architectures to override them and
    utilize that override to make them non-canonical addresses (thus
    causing #GP rather than #PF when dereferenced).
    
    Suggested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    master commit: 404227138e1e49c8073e946649a8d4173b35625c
    master date: 2014-11-17 15:05:53 +0100
---
 xen/include/asm-x86/config.h |    4 ++++
 xen/include/xen/list.h       |    9 ++++++---
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/xen/include/asm-x86/config.h b/xen/include/asm-x86/config.h
index 99d0e2c..3f7f852 100644
--- a/xen/include/asm-x86/config.h
+++ b/xen/include/asm-x86/config.h
@@ -101,6 +101,10 @@
 /* Return value for zero-size _xmalloc(), distinguished from NULL. */
 #define ZERO_BLOCK_PTR ((void *)0xBAD0BAD0BAD0BAD0UL)
 
+/* Override include/xen/list.h to make these non-canonical addresses. */
+#define LIST_POISON1  ((void *)0x0100100100100100UL)
+#define LIST_POISON2  ((void *)0x0200200200200200UL)
+
 #ifndef __ASSEMBLY__
 extern unsigned long trampoline_phys;
 #define bootsym_phys(sym)                                 \
diff --git a/xen/include/xen/list.h b/xen/include/xen/list.h
index 792eda3..9768fee 100644
--- a/xen/include/xen/list.h
+++ b/xen/include/xen/list.h
@@ -10,12 +10,15 @@
 #include <xen/lib.h>
 #include <asm/system.h>
 
-/* These are non-NULL pointers that will result in page faults
- * under normal circumstances, used to verify that nobody uses
- * non-initialized list entries.
+/*
+ * These are non-NULL pointers that will result in faults under normal
+ * circumstances, used to verify that nobody uses non-initialized list
+ * entries. Architectures can override these.
  */
+#ifndef LIST_POISON1
 #define LIST_POISON1  ((void *) 0x00100100)
 #define LIST_POISON2  ((void *) 0x00200200)
+#endif
 
 /*
  * Simple doubly linked list implementation.
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.4

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