[17/29] arm64: Kconfig: Add CONFIG_UNMAP_KERNEL_AT_EL0

Message ID	1519790211-16582-18-git-send-email-alex.shi@linaro.org
State	New
Headers	show Delivered-To: patch@linaro.org Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; From: Alex Shi <alex.shi@linaro.org> To: Marc Zyngier <marc.zyngier@arm.com>, Will Deacon <will.deacon@arm.com>, Ard Biesheuvel <ard.biesheuvel@linaro.org>, Catalin Marinas <catalin.marinas@arm.com>, stable@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Cc: Alex Shi <alex.shi@linaro.org> Subject: [PATCH 17/29] arm64: Kconfig: Add CONFIG_UNMAP_KERNEL_AT_EL0 Date: Wed, 28 Feb 2018 11:56:39 +0800 Message-Id: <1519790211-16582-18-git-send-email-alex.shi@linaro.org> In-Reply-To: <1519790211-16582-1-git-send-email-alex.shi@linaro.org> References: <1519790211-16582-1-git-send-email-alex.shi@linaro.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk
Series	arm meltdown fix backporting review for lts 4.9 \| expand [0/29] arm meltdown fix backporting review for lts 4.9 [02/29] arm64: mm: Move ASID from TTBR0 to TTBR1 [03/29] arm64: mm: Allocate ASIDs in pairs [04/29] arm64: mm: Add arm64_kernel_unmapped_at_el0 helper [05/29] arm64: mm: Invalidate both kernel and user ASIDs when performing TLBI [06/29] arm64: factor out entry stack manipulation [07/29] arm64: entry.S: move SError handling into a C function for future expansion [08/29] module: extend 'rodata=off' boot cmdline parameter to module mappings [09/29] arm64: entry: Add exception trampoline page for exceptions from EL0 [10/29] arm64: mm: Map entry trampoline into trampoline and kernel page tables [12/29] arm64: entry: Hook up entry trampoline to exception vectors [14/29] arm64: entry: Add fake CPU feature for unmapping the kernel at EL0 [15/29] arm64: kaslr: Put kernel vectors address in separate data page [16/29] arm64: use RET instruction for exiting the trampoline [17/29] arm64: Kconfig: Add CONFIG_UNMAP_KERNEL_AT_EL0 [18/29] arm64: Kconfig: Reword UNMAP_KERNEL_AT_EL0 kconfig entry [19/29] arm64: Take into account ID_AA64PFR0_EL1.CSV3 [20/29] arm64: Allow checking of a CPU-local erratum [21/29] arm64: capabilities: Handle duplicate entries for a capability [22/29] arm64: cputype: Add missing MIDR values for Cortex-A72 and Cortex-A75 [23/29] arm64: cputype: Add MIDR values for Cavium ThunderX2 CPUs [24/29] arm64: Turn on KPTI only on CPUs that need it [26/29] arm64: kpti: Add ->enable callback to remap swapper using nG mappings [27/29] arm64: Force KPTI to be disabled on Cavium ThunderX [28/29] arm64: entry: Reword comment about post_ttbr_update_workaround [29/29] arm64: idmap: Use "awx" flags for .idmap.text .pushsection directives

Message ID

1519790211-16582-18-git-send-email-alex.shi@linaro.org

State

New

Headers

Received-SPF: pass (google.com: best guess record for domain of
	linux-kernel-owner@vger.kernel.org designates 209.132.180.67
	as permitted sender) client-ip=209.132.180.67; 
From: Alex Shi <alex.shi@linaro.org>
To: Marc Zyngier <marc.zyngier@arm.com>, Will Deacon <will.deacon@arm.com>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	stable@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Cc: Alex Shi <alex.shi@linaro.org>
Subject: [PATCH 17/29] arm64: Kconfig: Add CONFIG_UNMAP_KERNEL_AT_EL0
Date: Wed, 28 Feb 2018 11:56:39 +0800
Message-Id: <1519790211-16582-18-git-send-email-alex.shi@linaro.org>
In-Reply-To: <1519790211-16582-1-git-send-email-alex.shi@linaro.org>
References: <1519790211-16582-1-git-send-email-alex.shi@linaro.org>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Series

arm meltdown fix backporting review for lts 4.9 | expand

Commit Message

Alex Shi Feb. 28, 2018, 3:56 a.m. UTC

From: Will Deacon <will.deacon@arm.com>


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 <labbott@redhat.com>

Tested-by: Shanker Donthineni <shankerd@codeaurora.org>

Signed-off-by: Will Deacon <will.deacon@arm.com>

Signed-off-by: Alex Shi <alex.shi@linaro.org>

---
 arch/arm64/Kconfig | 13 +++++++++++++
 1 file changed, 13 insertions(+)

-- 
2.7.4

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

[17/29] arm64: Kconfig: Add CONFIG_UNMAP_KERNEL_AT_EL0

Commit Message

Patch