diff options
| author | Avi Kivity <avi@qumranet.com> | 2008-05-20 14:39:25 +0300 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2008-05-20 13:42:31 +0200 |
| commit | 948f984df52511bb0efa5c026813b0c34de43aa0 (patch) | |
| tree | 942db22e4a7ed1eafe4785beec858b7e7c8a9ac5 | |
| parent | 8033c6e9736c29cce5f0d0abbca9a44dffb20c39 (diff) | |
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
permanently unmapped ranges.
Other 64-bit architectures will likely find similar unmapped ranges.
Signed-off-by: Avi Kivity <avi@qumranet.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
| -rw-r--r-- | arch/x86/Kconfig | 5 | ||||
| -rw-r--r-- | include/linux/poison.h | 10 |
2 files changed, 13 insertions, 2 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index fe361ae7ef2f..e21cc33b794a 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -1021,6 +1021,11 @@ config ARCH_MEMORY_PROBE def_bool X86_64 depends on MEMORY_HOTPLUG +config ILLEGAL_POINTER_VALUE + hex + default 0 if X86_32 + default 0xffffc10000000000 if X86_64 + source "mm/Kconfig" config HIGHPTE diff --git a/include/linux/poison.h b/include/linux/poison.h index 9f31683728fd..0d105a56e668 100644 --- a/include/linux/poison.h +++ b/include/linux/poison.h @@ -1,14 +1,20 @@ #ifndef _LINUX_POISON_H #define _LINUX_POISON_H +#ifdef CONFIG_ILLEGAL_POINTER_VALUE +#define POISON_POINTER_DELTA CONFIG_ILLEGAL_POINTER_VALUE +#else +#define POISON_POINTER_DELTA 0L +#endif + /********** include/linux/list.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. */ -#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 **********/ /* |