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authorAvi Kivity <avi@qumranet.com>2010-01-10 16:28:09 +0200
committerLinus Torvalds <torvalds@linux-foundation.org>2010-01-11 09:45:37 -0800
commita29815a333c6c6e677294bbe5958e771d0aad3fd (patch)
tree589a782f1992a7da55469379688deaa9f355b779 /include
parentc0f607c608ba889db5250235ba620f818aa44a4d (diff)
downloadlinux-linaro-android-a29815a333c6c6e677294bbe5958e771d0aad3fd.tar.gz
core, x86: make LIST_POISON less deadly
The list macros use LIST_POISON1 and LIST_POISON2 as undereferencable pointers in order to trap erronous use of freed list_heads. Unfortunately userspace can arrange for those pointers to actually be dereferencable, potentially turning an oops to an expolit. To avoid this allow architectures (currently x86_64 only) to override the default values for these pointers with truly-undereferencable values. This is easy on x86_64 as the virtual address space is large and contains areas that cannot be mapped. Other 64-bit architectures will likely find similar unmapped ranges. [ingo: switch to 0xdead000000000000 as the unmapped area] [ingo: add comments, cleanup] [jaswinder: eliminate sparse warnings] Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Avi Kivity <avi@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/poison.h16
1 files changed, 14 insertions, 2 deletions
diff --git a/include/linux/poison.h b/include/linux/poison.h
index 7fc194aef8c..2110a81c5e2 100644
--- a/include/linux/poison.h
+++ b/include/linux/poison.h
@@ -2,13 +2,25 @@
#define _LINUX_POISON_H
/********** include/linux/list.h **********/
+
+/*
+ * Architectures might want to move the poison pointer offset
+ * into some well-recognized area such as 0xdead000000000000,
+ * that is also not mappable by user-space exploits:
+ */
+#ifdef CONFIG_ILLEGAL_POINTER_VALUE
+# define POISON_POINTER_DELTA _AC(CONFIG_ILLEGAL_POINTER_VALUE, UL)
+#else
+# define POISON_POINTER_DELTA 0
+#endif
+
/*
* These are non-NULL pointers that will result in page faults
* under normal circumstances, used to verify that nobody uses
* non-initialized list entries.
*/
-#define LIST_POISON1 ((void *) 0x00100100)
-#define LIST_POISON2 ((void *) 0x00200200)
+#define LIST_POISON1 ((void *) 0x00100100 + POISON_POINTER_DELTA)
+#define LIST_POISON2 ((void *) 0x00200200 + POISON_POINTER_DELTA)
/********** include/linux/timer.h **********/
/*