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core, x86: make LIST_POISON less deadly

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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 <[email protected]>
Signed-off-by: Jaswinder Singh Rajput <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Signed-off-by: Avi Kivity <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Avi Kivity 2010-01-10 16:28:09 +02:00 • committed by Linus Torvalds
commit a29815a333
2 changed files with 19 additions and 2 deletions
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5
arch/x86/Kconfig
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@ -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