[v2] module: extend 'rodata=off' boot cmdline parameter to module mappings
diff mbox

Message ID 20161021011333.11411-1-takahiro.akashi@linaro.org
State New
Headers show

Commit Message

AKASHI Takahiro Oct. 21, 2016, 1:13 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: 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>
---
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      | 21 ++++++++++++++++++---
 3 files changed, 26 insertions(+), 5 deletions(-)

Comments

Mark Rutland Nov. 3, 2016, 4:17 p.m. UTC | #1
[Adding Jessica]

On Fri, Oct 21, 2016 at 10:13:33AM +0900, AKASHI Takahiro wrote:
> 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: 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>

FWIW:

Acked-by: Mark Rutland <mark.rutland@arm.com>

Thanks,
Mark.

> ---
> 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      | 21 ++++++++++++++++++---
>  3 files changed, 26 insertions(+), 5 deletions(-)
> 
> 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..34d1880 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 +1992,13 @@ 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_rodata(layout, set_memory_x);
> -	frob_ro_after_init(layout, set_memory_rw);
> +	if (rodata_enabled)
> +		frob_ro_after_init(layout, set_memory_rw);
>  	frob_ro_after_init(layout, set_memory_x);
>  	frob_writable_data(layout, set_memory_x);
>  }
> -- 
> 2.10.0
>
Jessica Yu Nov. 13, 2016, 3:04 a.m. UTC | #2
+++ AKASHI Takahiro [21/10/16 10:13 +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: 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>
>---
>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      | 21 ++++++++++++++++++---
> 3 files changed, 26 insertions(+), 5 deletions(-)
>
>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..34d1880 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 +1992,13 @@ 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_rodata(layout, set_memory_x);
>-	frob_ro_after_init(layout, set_memory_rw);
>+	if (rodata_enabled)
>+		frob_ro_after_init(layout, set_memory_rw);

Why not merge this hunk with the previous if (rodata_enabled) check?
I think it's more readable that way. In any case, the rest of the
patch looks good to me.

Jessica
AKASHI Takahiro Nov. 14, 2016, 6:12 a.m. UTC | #3
On Sat, Nov 12, 2016 at 07:04:22PM -0800, Jessica Yu wrote:
> +++ AKASHI Takahiro [21/10/16 10:13 +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: 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>
> >---
> >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      | 21 ++++++++++++++++++---
> >3 files changed, 26 insertions(+), 5 deletions(-)
> >
> >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..34d1880 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 +1992,13 @@ 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_rodata(layout, set_memory_x);
> >-	frob_ro_after_init(layout, set_memory_rw);
> >+	if (rodata_enabled)
> >+		frob_ro_after_init(layout, set_memory_rw);
> 
> Why not merge this hunk with the previous if (rodata_enabled) check?
> I think it's more readable that way. In any case, the rest of the
> patch looks good to me.

Sure. See my v3.

Thanks,
-Takahiro AKASHI

> Jessica

Patch
diff mbox

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..34d1880 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 +1992,13 @@  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_rodata(layout, set_memory_x);
-	frob_ro_after_init(layout, set_memory_rw);
+	if (rodata_enabled)
+		frob_ro_after_init(layout, set_memory_rw);
 	frob_ro_after_init(layout, set_memory_x);
 	frob_writable_data(layout, set_memory_x);
 }