[PATCH v11 7/9] powerpc: Set ARCH_HAS_STRICT_MODULE_RWX

[Jordan Niethe <jniethe5@gmail.com>]

From: Russell Currey <ruscur@russell.cc>

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.

With STRICT_MODULE_RWX, now make module_alloc() allocate pages with
KERNEL_PAGE protection rather than KERNEL_PAGE_EXEC.

Book32s/32 processors with a hash mmu (i.e. 604 core) can not set memory
protection on a page by page basis so do not enable.

Signed-off-by: Russell Currey <ruscur@russell.cc>
[jpn: - predicate on !PPC_BOOK3S_604
      - make module_alloc() use PAGE_KERNEL protection]
Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
---
v10: - Predicate on !PPC_BOOK3S_604
     - Make module_alloc() use PAGE_KERNEL protection
v11: - Neaten up
---
 arch/powerpc/Kconfig         | 1 +
 arch/powerpc/kernel/module.c | 9 ++++++---
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 94c34932a74b..9e264309fd99 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -140,6 +140,7 @@ 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_604
 	select ARCH_HAS_TICK_BROADCAST		if GENERIC_CLOCKEVENTS_BROADCAST
 	select ARCH_HAS_UACCESS_FLUSHCACHE
 	select ARCH_HAS_COPY_MC			if PPC64
diff --git a/arch/powerpc/kernel/module.c b/arch/powerpc/kernel/module.c
index c60c7457ff47..9eabaf1fadbe 100644
--- a/arch/powerpc/kernel/module.c
+++ b/arch/powerpc/kernel/module.c
@@ -92,9 +92,12 @@ int module_finalize(const Elf_Ehdr *hdr,
 static __always_inline void *
 __module_alloc(unsigned long size, unsigned long start, unsigned long end)
 {
-	return __vmalloc_node_range(size, 1, start, end, GFP_KERNEL,
-				    PAGE_KERNEL_EXEC, VM_FLUSH_RESET_PERMS, NUMA_NO_NODE,
-				    __builtin_return_address(0));
+	pgprot_t prot = IS_ENABLED(CONFIG_STRICT_MODULE_RWX) ? PAGE_KERNEL :
+							       PAGE_KERNEL_EXEC;
+
+	return __vmalloc_node_range(size, 1, MODULES_VADDR, MODULES_END,
+			GFP_KERNEL, prot, VM_FLUSH_RESET_PERMS,
+			NUMA_NO_NODE, __builtin_return_address(0));
 }
 
 void *module_alloc(unsigned long size)
-- 
2.25.1