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.

Book3s/32 603 and 604 core processors are not able to write protect
kernel pages so do not set ARCH_HAS_STRICT_MODULE_RWX for Book3s/32.

[jpn: - predicate on !PPC_BOOK3S_604
      - make module_alloc() use PAGE_KERNEL protection]

Signed-off-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210609013431.9805-8-jniethe5@gmail.com

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index abfe2e9225fae424dd939b648201492a876c38d3..72f307f1796be2820a199ce0c66364cdec6611bf 100644 (file)
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -142,6 +142,7 @@ 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) && !HIBERNATION)
+       select ARCH_HAS_STRICT_MODULE_RWX       if ARCH_HAS_STRICT_KERNEL_RWX && !PPC_BOOK3S_32
        select ARCH_HAS_TICK_BROADCAST          if GENERIC_CLOCKEVENTS_BROADCAST
        select ARCH_HAS_UACCESS_FLUSHCACHE
        select ARCH_HAS_UBSAN_SANITIZE_ALL
@@ -267,6 +268,7 @@ config PPC
        select PPC_DAWR                         if PPC64
        select RTC_LIB
        select SPARSE_IRQ
+       select STRICT_KERNEL_RWX if STRICT_MODULE_RWX
        select SYSCTL_EXCEPTION_TRACE
        select THREAD_INFO_IN_TASK
        select VIRT_TO_BUS                      if !PPC64