[PATCH 17/29] arm64: Kconfig: Add CONFIG_UNMAP_KERNEL_AT_EL0
From: Alex Shi <hidden>
Date: 2018-02-28 03:59:43
Also in:
lkml, stable
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
From: Will Deacon <redacted> commit 084eb77cd3a8 upstream. Add a Kconfig entry to control use of the entry trampoline, which allows us to unmap the kernel whilst running in userspace and improve the robustness of KASLR. Reviewed-by: Mark Rutland <mark.rutland@arm.com> Tested-by: Laura Abbott <redacted> Tested-by: Shanker Donthineni <redacted> Signed-off-by: Will Deacon <redacted> Signed-off-by: Alex Shi <redacted> --- arch/arm64/Kconfig | 13 +++++++++++++ 1 file changed, 13 insertions(+)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 7769c2e..6b6e9f8 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig@@ -733,6 +733,19 @@ config FORCE_MAX_ZONEORDER However for 4K, we choose a higher default value, 11 as opposed to 10, giving us 4M allocations matching the default size used by generic code. +config UNMAP_KERNEL_AT_EL0 + bool "Unmap kernel when running in userspace (aka \"KAISER\")" + default y + help + Some attacks against KASLR make use of the timing difference between + a permission fault which could arise from a page table entry that is + present in the TLB, and a translation fault which always requires a + page table walk. This option defends against these attacks by unmapping + the kernel whilst running in userspace, therefore forcing translation + faults for all of kernel space. + + If unsure, say Y. + menuconfig ARMV8_DEPRECATED bool "Emulate deprecated/obsolete ARMv8 instructions" depends on COMPAT
--
2.7.4