Commit 39290b38 authored by AKASHI Takahiro's avatar AKASHI Takahiro Committed by Jessica Yu
Browse files

module: extend 'rodata=off' boot cmdline parameter to module mappings 



The current "rodata=off" parameter disables read-only kernel mappings
under CONFIG_DEBUG_RODATA:
    commit d2aa1aca ("mm/init: Add 'rodata=off' boot cmdline parameter
    to disable read-only kernel mappings")

This patch is a logical extension to module mappings ie. read-only mappings
at module loading can be disabled even if CONFIG_DEBUG_SET_MODULE_RONX
(mainly for debug use). Please note, however, that it only affects RO/RW
permissions, keeping NX set.

This is the first step to make CONFIG_DEBUG_SET_MODULE_RONX mandatory
(always-on) in the future as CONFIG_DEBUG_RODATA on x86 and arm64.

Suggested-by: default avatarand Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarAKASHI Takahiro <takahiro.akashi@linaro.org>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Acked-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Link: http://lkml.kernel.org/r/20161114061505.15238-1-takahiro.akashi@linaro.org


Signed-off-by: default avatarJessica Yu <jeyu@redhat.com>
parent 71d9f507

include/linux/init.h

+3 −0
Original line number Diff line number Diff line
@@ -126,6 +126,9 @@ void prepare_namespace(void); 
void __init load_default_modules(void);

int __init init_rootfs(void);



#if defined(CONFIG_DEBUG_RODATA) || defined(CONFIG_DEBUG_SET_MODULE_RONX)

extern bool rodata_enabled;

#endif

#ifdef CONFIG_DEBUG_RODATA

void mark_rodata_ro(void);

#endif

init/main.c

+5 −2
Original line number Diff line number Diff line
@@ -81,6 +81,7 @@ 
#include <linux/integrity.h>

#include <linux/proc_ns.h>

#include <linux/io.h>

#include <linux/cache.h>



#include <asm/io.h>

#include <asm/bugs.h>
@@ -914,14 +915,16 @@ static int try_to_run_init_process(const char *init_filename) 


static noinline void __init kernel_init_freeable(void);



#ifdef CONFIG_DEBUG_RODATA

static bool rodata_enabled = true;

#if defined(CONFIG_DEBUG_RODATA) || defined(CONFIG_SET_MODULE_RONX)

bool rodata_enabled __ro_after_init = true;

static int __init set_debug_rodata(char *str)

{

	return strtobool(str, &rodata_enabled);

}

__setup("rodata=", set_debug_rodata);

#endif



#ifdef CONFIG_DEBUG_RODATA

static void mark_readonly(void)

{

	if (rodata_enabled)

kernel/module.c

+17 −3
Original line number Diff line number Diff line
@@ -1902,6 +1902,9 @@ static void frob_writable_data(const struct module_layout *layout, 
/* livepatching wants to disable read-only so it can frob module. */

void module_disable_ro(const struct module *mod)

{

	if (!rodata_enabled)

		return;



	frob_text(&mod->core_layout, set_memory_rw);

	frob_rodata(&mod->core_layout, set_memory_rw);

	frob_ro_after_init(&mod->core_layout, set_memory_rw);
@@ -1911,6 +1914,9 @@ void module_disable_ro(const struct module *mod) 


void module_enable_ro(const struct module *mod, bool after_init)

{

	if (!rodata_enabled)

		return;



	frob_text(&mod->core_layout, set_memory_ro);

	frob_rodata(&mod->core_layout, set_memory_ro);

	frob_text(&mod->init_layout, set_memory_ro);
@@ -1943,6 +1949,9 @@ void set_all_modules_text_rw(void) 
{

	struct module *mod;



	if (!rodata_enabled)

		return;



	mutex_lock(&module_mutex);

	list_for_each_entry_rcu(mod, &modules, list) {

		if (mod->state == MODULE_STATE_UNFORMED)
@@ -1959,6 +1968,9 @@ void set_all_modules_text_ro(void) 
{

	struct module *mod;



	if (!rodata_enabled)

		return;



	mutex_lock(&module_mutex);

	list_for_each_entry_rcu(mod, &modules, list) {

		/*
@@ -1978,10 +1990,12 @@ void set_all_modules_text_ro(void) 


static void disable_ro_nx(const struct module_layout *layout)

{

	if (rodata_enabled) {

		frob_text(layout, set_memory_rw);

		frob_rodata(layout, set_memory_rw);

	frob_rodata(layout, set_memory_x);

		frob_ro_after_init(layout, set_memory_rw);

	}

	frob_rodata(layout, set_memory_x);

	frob_ro_after_init(layout, set_memory_x);

	frob_writable_data(layout, set_memory_x);

}

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