diff options
| author | Avi Kivity | 2010-01-10 16:28:09 +0200 |
|---|---|---|
| committer | Linus Torvalds | 2010-01-11 09:45:37 -0800 |
| commit | a29815a333c6c6e677294bbe5958e771d0aad3fd (patch) | |
| tree | 589a782f1992a7da55469379688deaa9f355b779 | |
| parent | c0f607c608ba889db5250235ba620f818aa44a4d (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
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>
| -rw-r--r-- | arch/x86/Kconfig | 5 | ||||
| -rw-r--r-- | include/linux/poison.h | 16 |
2 files changed, 19 insertions, 2 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 6bf1f1ac478c..cbcbfdee3ee0 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -1247,6 +1247,11 @@ config ARCH_MEMORY_PROBE def_bool X86_64 depends on MEMORY_HOTPLUG +config ILLEGAL_POINTER_VALUE + hex + default 0 if X86_32 + default 0xdead000000000000 if X86_64 + source "mm/Kconfig" config HIGHPTE diff --git a/include/linux/poison.h b/include/linux/poison.h index 7fc194aef8c2..2110a81c5e2a 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 **********/ /* |