Commit f6853eb5 authored Nov 15, 2016 by Michael Ellerman

powerpc/64: Define ILLEGAL_POINTER_VALUE for 64-bit

This is used in poison.h to offset poison values so that they don't
point directly into user space.

The value we choose sits roughly between user and kernel space, which
means on their own the poison values don't point anywhere useful. If an
attacker can cause an access at some offset from the poison value then
we may still be in trouble, but by putting the poison values between
user and kernel space we maximise the required size of that offset.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

parent 93c2ec0f

arch/powerpc/Kconfig

+7 −0

Original line number	Diff line number	Diff line
		@@ -580,6 +580,13 @@ config ARCH_SPARSEMEM_DEFAULT
		config SYS_SUPPORTS_HUGETLBFS
		bool

		config ILLEGAL_POINTER_VALUE
		hex
		# This is roughly half way between the top of user space and the bottom
		# of kernel space, which seems about as good as we can get.
		default 0x5deadbeef0000000 if PPC64
		default 0

		source "mm/Kconfig"

		config ARCH_MEMORY_PROBE