diff mbox

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

Message ID 20161020062458.14014-1-takahiro.akashi@linaro.org
State New
Headers show

Commit Message

AKASHI Takahiro Oct. 20, 2016, 6:24 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>

Cc: Rusty Russell <rusty@rustcorp.com.au>
---
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          |  2 +-
 kernel/module.c      | 21 ++++++++++++++++++---
 3 files changed, 21 insertions(+), 5 deletions(-)

-- 
2.10.0

Comments

Kees Cook Oct. 20, 2016, 8:48 p.m. UTC | #1 
On Wed, Oct 19, 2016 at 11:24 PM, AKASHI Takahiro
<takahiro.akashi@linaro.org> 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>

> Cc: Rusty Russell <rusty@rustcorp.com.au>

> ---

> 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          |  2 +-

>  kernel/module.c      | 21 ++++++++++++++++++---

>  3 files changed, 21 insertions(+), 5 deletions(-)

>

> diff --git a/include/linux/init.h b/include/linux/init.h

> index e30104c..20aa2eb 100644

> --- a/include/linux/init.h

> +++ b/include/linux/init.h

> @@ -126,7 +126,8 @@ void prepare_namespace(void);

>  void __init load_default_modules(void);

>  int __init init_rootfs(void);

>

> -#ifdef CONFIG_DEBUG_RODATA

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

> +extern bool rodata_enabled;

>  void mark_rodata_ro(void);

>  #endif

>

> diff --git a/init/main.c b/init/main.c

> index 2858be7..92db2f3 100644

> --- a/init/main.c

> +++ b/init/main.c

> @@ -915,7 +915,7 @@ 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;

> +bool rodata_enabled = true;


Is there a mismatch here between the extern ifdef and the bool ifdef?
I.e. shouldn't the ifdef here be || DEBUG_SET_MODULE_RONX too?

Also, can you mark this as __ro_after_init, since nothing changes it
after the kernel command line is parsed?

Otherwise, this looks fine to me.

-Kees


-- 
Kees Cook
Nexus Security
AKASHI Takahiro Oct. 21, 2016, 1:12 a.m. UTC | #2 
On Thu, Oct 20, 2016 at 01:48:15PM -0700, Kees Cook wrote:
> On Wed, Oct 19, 2016 at 11:24 PM, AKASHI Takahiro

> <takahiro.akashi@linaro.org> 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>

> > Cc: Rusty Russell <rusty@rustcorp.com.au>

> > ---

> > 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          |  2 +-

> >  kernel/module.c      | 21 ++++++++++++++++++---

> >  3 files changed, 21 insertions(+), 5 deletions(-)

> >

> > diff --git a/include/linux/init.h b/include/linux/init.h

> > index e30104c..20aa2eb 100644

> > --- a/include/linux/init.h

> > +++ b/include/linux/init.h

> > @@ -126,7 +126,8 @@ void prepare_namespace(void);

> >  void __init load_default_modules(void);

> >  int __init init_rootfs(void);

> >

> > -#ifdef CONFIG_DEBUG_RODATA

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

> > +extern bool rodata_enabled;

> >  void mark_rodata_ro(void);

> >  #endif

> >

> > diff --git a/init/main.c b/init/main.c

> > index 2858be7..92db2f3 100644

> > --- a/init/main.c

> > +++ b/init/main.c

> > @@ -915,7 +915,7 @@ 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;

> > +bool rodata_enabled = true;

> 

> Is there a mismatch here between the extern ifdef and the bool ifdef?

> I.e. shouldn't the ifdef here be || DEBUG_SET_MODULE_RONX too?


Yes.

> Also, can you mark this as __ro_after_init, since nothing changes it

> after the kernel command line is parsed?


Yes, yes.

Thanks,
-Takahiro AKASHI

> Otherwise, this looks fine to me.

> 

> -Kees

> 

> 

> -- 

> Kees Cook

> Nexus Security
Rusty Russell Oct. 26, 2016, 12:13 a.m. UTC | #3 
AKASHI Takahiro <takahiro.akashi@linaro.org> writes:
> On Thu, Oct 20, 2016 at 01:48:15PM -0700, Kees Cook wrote:

>> On Wed, Oct 19, 2016 at 11:24 PM, AKASHI Takahiro

>> <takahiro.akashi@linaro.org> 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 patch looks good (except the minor issues noted by Kees); please CC
the followup version to Jessica as new module maintainer.

Thanks!
Rusty.

>> >

>> > 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>

>> > Cc: Rusty Russell <rusty@rustcorp.com.au>

>> > ---

>> > 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          |  2 +-

>> >  kernel/module.c      | 21 ++++++++++++++++++---

>> >  3 files changed, 21 insertions(+), 5 deletions(-)

>> >

>> > diff --git a/include/linux/init.h b/include/linux/init.h

>> > index e30104c..20aa2eb 100644

>> > --- a/include/linux/init.h

>> > +++ b/include/linux/init.h

>> > @@ -126,7 +126,8 @@ void prepare_namespace(void);

>> >  void __init load_default_modules(void);

>> >  int __init init_rootfs(void);

>> >

>> > -#ifdef CONFIG_DEBUG_RODATA

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

>> > +extern bool rodata_enabled;

>> >  void mark_rodata_ro(void);

>> >  #endif

>> >

>> > diff --git a/init/main.c b/init/main.c

>> > index 2858be7..92db2f3 100644

>> > --- a/init/main.c

>> > +++ b/init/main.c

>> > @@ -915,7 +915,7 @@ 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;

>> > +bool rodata_enabled = true;

>> 

>> Is there a mismatch here between the extern ifdef and the bool ifdef?

>> I.e. shouldn't the ifdef here be || DEBUG_SET_MODULE_RONX too?

>

> Yes.

>

>> Also, can you mark this as __ro_after_init, since nothing changes it

>> after the kernel command line is parsed?

>

> Yes, yes.

>

> Thanks,

> -Takahiro AKASHI

>

>> Otherwise, this looks fine to me.

>> 

>> -Kees

>> 

>> 

>> -- 

>> Kees Cook

>> Nexus Security
AKASHI Takahiro Oct. 26, 2016, 4:43 a.m. UTC | #4 
Rusty, Jessica

On Wed, Oct 26, 2016 at 10:43:32AM +1030, Rusty Russell wrote:
> AKASHI Takahiro <takahiro.akashi@linaro.org> writes:

> > On Thu, Oct 20, 2016 at 01:48:15PM -0700, Kees Cook wrote:

> >> On Wed, Oct 19, 2016 at 11:24 PM, AKASHI Takahiro

> >> <takahiro.akashi@linaro.org> 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 patch looks good (except the minor issues noted by Kees); please CC

> the followup version to Jessica as new module maintainer.


I think that the new version (v2)[1] addresses Kees' comments already.

[1] http://lkml.iu.edu//hypermail/linux/kernel/1610.2/04163.html

Thanks,
-Takahiro AKASHI

> Thanks!

> Rusty.

> 

> >> >

> >> > 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>

> >> > Cc: Rusty Russell <rusty@rustcorp.com.au>

> >> > ---

> >> > 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          |  2 +-

> >> >  kernel/module.c      | 21 ++++++++++++++++++---

> >> >  3 files changed, 21 insertions(+), 5 deletions(-)

> >> >

> >> > diff --git a/include/linux/init.h b/include/linux/init.h

> >> > index e30104c..20aa2eb 100644

> >> > --- a/include/linux/init.h

> >> > +++ b/include/linux/init.h

> >> > @@ -126,7 +126,8 @@ void prepare_namespace(void);

> >> >  void __init load_default_modules(void);

> >> >  int __init init_rootfs(void);

> >> >

> >> > -#ifdef CONFIG_DEBUG_RODATA

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

> >> > +extern bool rodata_enabled;

> >> >  void mark_rodata_ro(void);

> >> >  #endif

> >> >

> >> > diff --git a/init/main.c b/init/main.c

> >> > index 2858be7..92db2f3 100644

> >> > --- a/init/main.c

> >> > +++ b/init/main.c

> >> > @@ -915,7 +915,7 @@ 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;

> >> > +bool rodata_enabled = true;

> >> 

> >> Is there a mismatch here between the extern ifdef and the bool ifdef?

> >> I.e. shouldn't the ifdef here be || DEBUG_SET_MODULE_RONX too?

> >

> > Yes.

> >

> >> Also, can you mark this as __ro_after_init, since nothing changes it

> >> after the kernel command line is parsed?

> >

> > Yes, yes.

> >

> > Thanks,

> > -Takahiro AKASHI

> >

> >> Otherwise, this looks fine to me.

> >> 

> >> -Kees

> >> 

> >> 

> >> -- 

> >> Kees Cook

> >> Nexus Security
diff mbox

Patch

diff --git a/include/linux/init.h b/include/linux/init.h
index e30104c..20aa2eb 100644
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -126,7 +126,8 @@  void prepare_namespace(void);
 void __init load_default_modules(void);
 int __init init_rootfs(void);
 
-#ifdef CONFIG_DEBUG_RODATA
+#if defined(CONFIG_DEBUG_RODATA) || defined(CONFIG_DEBUG_SET_MODULE_RONX)
+extern bool rodata_enabled;
 void mark_rodata_ro(void);
 #endif
 
diff --git a/init/main.c b/init/main.c
index 2858be7..92db2f3 100644
--- a/init/main.c
+++ b/init/main.c
@@ -915,7 +915,7 @@  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;
+bool rodata_enabled = true;
 static int __init set_debug_rodata(char *str)
 {
 	return strtobool(str, &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);
 }