diff mbox

[v3] module: extend 'rodata=off' boot cmdline parameter to module mappings

Message ID 20161114061505.15238-1-takahiro.akashi@linaro.org (mailing list archive)
State New, archived
Headers show

Commit Message

AKASHI Takahiro Nov. 14, 2016, 6:15 a.m. UTC
The current "rodata=off" parameter disables read-only kernel mappings
under CONFIG_DEBUG_RODATA:
    commit d2aa1acad22f ("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>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Jessica Yu <jeyu@redhat.com>
---
v3:
  * merge if-statements in disable_ro_nx()
v2:
  * use CONFIG_DEBUG_RODATA/SET_MODULE_RONX guards better where appropriate
  * make "rodata_enabled" variable as __ro_after_init
v1:
  * remove RFC's "module_ronx=" and merge it with "rodata="
  * always keep NX set if CONFIG_SET_MODULE_RONX

 include/linux/init.h |  3 +++
 init/main.c          |  7 +++++--
 kernel/module.c      | 20 +++++++++++++++++---
 3 files changed, 25 insertions(+), 5 deletions(-)

Comments

Jessica Yu Nov. 25, 2016, 5:48 a.m. UTC | #1
+++ AKASHI Takahiro [14/11/16 15:15 +0900]:
>The current "rodata=off" parameter disables read-only kernel mappings
>under CONFIG_DEBUG_RODATA:
>    commit d2aa1acad22f ("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>
>Cc: Rusty Russell <rusty@rustcorp.com.au>

Hi Rusty, could I get an (n)ack for this patch? :-)

Thanks!

Jessica
Rusty Russell Nov. 28, 2016, midnight UTC | #2
Jessica Yu <jeyu@redhat.com> writes:

> +++ AKASHI Takahiro [14/11/16 15:15 +0900]:
>>The current "rodata=off" parameter disables read-only kernel mappings
>>under CONFIG_DEBUG_RODATA:
>>    commit d2aa1acad22f ("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>
>>Cc: Rusty Russell <rusty@rustcorp.com.au>
>
> Hi Rusty, could I get an (n)ack for this patch? :-)

Acked-by: Rusty Russell <rusty@rustcorp.com.au>

Cheers,
Rusty.
diff mbox

Patch

diff --git a/include/linux/init.h b/include/linux/init.h
index e30104c..885c3e6 100644
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -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
diff --git a/init/main.c b/init/main.c
index 2858be7..959a242 100644
--- a/init/main.c
+++ b/init/main.c
@@ -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)
diff --git a/kernel/module.c b/kernel/module.c
index f57dd63..6ad4b3f 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1910,6 +1910,9 @@  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);
@@ -1919,6 +1922,9 @@  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);
@@ -1951,6 +1957,9 @@  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)
@@ -1967,6 +1976,9 @@  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) {
 		if (mod->state == MODULE_STATE_UNFORMED)
@@ -1980,10 +1992,12 @@  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);
 }