kernel-hardening - [PATCH v5 4/5] powerpc: Set ARCH_HAS_STRICT_MODULE

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Date: Wed, 30 Oct 2019 18:31:10 +1100
From: Russell Currey <ruscur@...sell.cc>
To: linuxppc-dev@...ts.ozlabs.org
Cc: Russell Currey <ruscur@...sell.cc>,
	christophe.leroy@....fr,
	joel@....id.au,
	mpe@...erman.id.au,
	ajd@...ux.ibm.com,
	dja@...ens.net,
	npiggin@...il.com,
	kernel-hardening@...ts.openwall.com
Subject: [PATCH v5 4/5] powerpc: Set ARCH_HAS_STRICT_MODULE_RWX

To enable strict module RWX on powerpc, set:

    CONFIG_STRICT_MODULE_RWX=y

You should also have CONFIG_STRICT_KERNEL_RWX=y set to have any real
security benefit.

ARCH_HAS_STRICT_MODULE_RWX is set to require ARCH_HAS_STRICT_KERNEL_RWX.
This is due to a quirk in arch/Kconfig and arch/powerpc/Kconfig that
makes STRICT_MODULE_RWX *on by default* in configurations where
STRICT_KERNEL_RWX is *unavailable*.

Since this doesn't make much sense, and module RWX without kernel RWX
doesn't make much sense, having the same dependencies as kernel RWX
works around this problem.

Signed-off-by: Russell Currey <ruscur@...sell.cc>
---
This means that Daniel's test on book3e64 is pretty useless since we've
gone from being unable to turn it *off* to being unable to turn it *on*.

I think this is the right course of action for now.

 arch/powerpc/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 8f7005f0d097..52028e27f2d3 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -135,6 +135,7 @@ config PPC
 	select ARCH_HAS_SCALED_CPUTIME		if VIRT_CPU_ACCOUNTING_NATIVE && PPC_BOOK3S_64
 	select ARCH_HAS_SET_MEMORY
 	select ARCH_HAS_STRICT_KERNEL_RWX	if ((PPC_BOOK3S_64 || PPC32) && !RELOCATABLE && !HIBERNATION)
+	select ARCH_HAS_STRICT_MODULE_RWX	if ARCH_HAS_STRICT_KERNEL_RWX
 	select ARCH_HAS_TICK_BROADCAST		if GENERIC_CLOCKEVENTS_BROADCAST
 	select ARCH_HAS_UACCESS_FLUSHCACHE
 	select ARCH_HAS_UACCESS_MCSAFE		if PPC64
-- 
2.23.0

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