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Message-ID: <20180306112241.GA5938@pjb1027-Latitude-E5410>
Date: Tue, 6 Mar 2018 20:22:41 +0900
From: Jinbum Park <jinb.park7@...il.com>
To: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
kernel-hardening@...ts.openwall.com
Cc: gregkh@...uxfoundation.org, vladimir.murzin@....com,
keescook@...omium.org, will.deacon@....com, mark.rutland@....com,
catalin.marinas@....com
Subject: [PATCH] arm: mm: Kconfig: Disable KUSER_HELPERS in ARMv6 or later as
default
Codes for KUSER_HELPERS can be abused as ROP gadaget,
So that It's better to disable that as if possible.
Since over ARMv6 has ldrex/strex at user-space,
NEED_KUSER_HELPERS is not selected for over ARMv6.
But, Even though NEED_KUSER_HELPERS is not selected,
current configuration enable KUSER_HELPERS as default.
* as-is
- Enable KUSER_HELPERS as default even though over ARMv6.
- User can disable KUSER_HELPERS.
* to-be
- Disable KUSER_HELPERS in ARMv6 or later as default.
- User can enable KUSER_HELPERS for compatibility.
This change removes the unnecessary configuration that has security-risk.
Signed-off-by: Jinbum Park <jinb.park7@...il.com>
---
arch/arm/mm/Kconfig | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index 7f14acf..40e5fe5 100644
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@@ -840,7 +840,7 @@ config NEED_KUSER_HELPERS
config KUSER_HELPERS
bool "Enable kuser helpers in vector page" if !NEED_KUSER_HELPERS
depends on MMU
- default y
+ default y if NEED_KUSER_HELPERS
help
Warning: disabling this option may break user programs.
--
1.9.1
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