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

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The current "rodata=off" parameter disables read-only kernel mappings
under CONFIG_DEBUG_RODATA:
    commit d2aa1acad2 ("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: and Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Link: http://lkml.kernel.org/r/20161114061505.15238-1-takahiro.akashi@linaro.org
Signed-off-by: Jessica Yu <jeyu@redhat.com>
This commit is contained in:
AKASHI Takahiro 2016-11-14 15:15:05 +09:00 committed by Jessica Yu
parent 71d9f50793
commit 39290b389e
3 changed files with 25 additions and 5 deletions
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3
include/linux/init.h
View file

@ -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

7
init/main.c
View file

@ -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)

20
kernel/module.c
View file

@ -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)
{
frob_text(layout, set_memory_rw);
frob_rodata(layout, set_memory_rw);
if (rodata_enabled) {
frob_text(layout, set_memory_rw);
frob_rodata(layout, set_memory_rw);
frob_ro_after_init(layout, set_memory_rw);
}
frob_rodata(layout, set_memory_x);
frob_ro_after_init(layout, set_memory_rw);
frob_ro_after_init(layout, set_memory_x);
frob_writable_data(layout, set_memory_x);
}