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Message-Id: <1211125094-32167-1-git-send-email-avi@qumranet.com> Date: Sun, 18 May 2008 18:38:14 +0300 From: Avi Kivity <avi@...ranet.com> To: Andrew Morton <akpm@...l.org> Cc: Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org Subject: [PATCH] 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-undereferncable values. This is easy on x86_64 as the virtual address space is smaller than the range spanned by pointer values. Signed-off-by: Avi Kivity <avi@...ranet.com> --- arch/x86/Kconfig | 1 + include/asm-x86/poison.h | 14 ++++++++++++++ include/linux/poison.h | 4 ++++ lib/Kconfig | 3 +++ 4 files changed, 22 insertions(+), 0 deletions(-) create mode 100644 include/asm-x86/poison.h diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index fe361ae..0eb34a9 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -25,6 +25,7 @@ config X86 select HAVE_KRETPROBES select HAVE_KVM if ((X86_32 && !X86_VOYAGER && !X86_VISWS && !X86_NUMAQ) || X86_64) select HAVE_ARCH_KGDB if !X86_VOYAGER + select HAVE_ARCH_POISON config DEFCONFIG_LIST string diff --git a/include/asm-x86/poison.h b/include/asm-x86/poison.h new file mode 100644 index 0000000..26b95dd --- /dev/null +++ b/include/asm-x86/poison.h @@ -0,0 +1,14 @@ +#ifndef _ASM_X86_POISON_H +#define _ASM_X86_POISON_H + +/* + * Define LIST_POISON[12] as pointers that cannot be dereferenced. + */ +#ifdef CONFIG_X86_84 +# undef LIST_POISON1 +# undef LIST_POISON2 +# define LIST_POISON1 ((void *)0x8001000100010001L) +# define LIST_POISON2 ((void *)0x8002000200020002L) +#endif + +#endif diff --git a/include/linux/poison.h b/include/linux/poison.h index 9f31683..8bb6ad9 100644 --- a/include/linux/poison.h +++ b/include/linux/poison.h @@ -68,4 +68,8 @@ /********** sound/oss/ **********/ #define OSS_POISON_FREE 0xAB +#ifdef CONFIG_HAVE_ARCH_POISON +#include <asm/poison.h> +#endif + #endif diff --git a/lib/Kconfig b/lib/Kconfig index 8cc8e87..31b9457 100644 --- a/lib/Kconfig +++ b/lib/Kconfig @@ -150,4 +150,7 @@ config CHECK_SIGNATURE config HAVE_LMB boolean +config HAVE_ARCH_POISON + boolean + endmenu -- 1.5.5.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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