'struct kobj_type' is not modified in this driver. It is only used with
kobject_init_and_add() which takes a "const struct kobj_type *" parameter.

Constifying this structure moves some data to a read-only section, so
increase overall security.

On a x86_64, with allmodconfig:
Before:
======
   text	   data	    bss	    dec	    hex	filename
  22403	   4184	     24	  26611	   67f3	fs/nilfs2/sysfs.o

After:
=====
   text	   data	    bss	    dec	    hex	filename
  22723	   3928	     24	  26675	   6833	fs/nilfs2/sysfs.o

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
---
Compile tested-only
---
 fs/nilfs2/sysfs.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/nilfs2/sysfs.c b/fs/nilfs2/sysfs.c
index 379d22e28ed6..a5569b7f47a3 100644
--- a/fs/nilfs2/sysfs.c
+++ b/fs/nilfs2/sysfs.c
@@ -56,7 +56,7 @@ static void nilfs_##name##_attr_release(struct kobject *kobj) \
 						sg_##name##_kobj); \
 	complete(&subgroups->sg_##name##_kobj_unregister); \
 } \
-static struct kobj_type nilfs_##name##_ktype = { \
+static const struct kobj_type nilfs_##name##_ktype = { \
 	.default_groups	= nilfs_##name##_groups, \
 	.sysfs_ops	= &nilfs_##name##_attr_ops, \
 	.release	= nilfs_##name##_attr_release, \
@@ -166,7 +166,7 @@ static const struct sysfs_ops nilfs_snapshot_attr_ops = {
 	.store	= nilfs_snapshot_attr_store,
 };
 
-static struct kobj_type nilfs_snapshot_ktype = {
+static const struct kobj_type nilfs_snapshot_ktype = {
 	.default_groups	= nilfs_snapshot_groups,
 	.sysfs_ops	= &nilfs_snapshot_attr_ops,
 	.release	= nilfs_snapshot_attr_release,
@@ -967,7 +967,7 @@ static const struct sysfs_ops nilfs_dev_attr_ops = {
 	.store	= nilfs_dev_attr_store,
 };
 
-static struct kobj_type nilfs_dev_ktype = {
+static const struct kobj_type nilfs_dev_ktype = {
 	.default_groups	= nilfs_dev_groups,
 	.sysfs_ops	= &nilfs_dev_attr_ops,
 	.release	= nilfs_dev_attr_release,
-- 
2.45.2

On Sun, Jul 7, 2024 at 11:01 PM Christophe JAILLET wrote:
>
> 'struct kobj_type' is not modified in this driver. It is only used with
> kobject_init_and_add() which takes a "const struct kobj_type *" parameter.
>
> Constifying this structure moves some data to a read-only section, so
> increase overall security.
>
> On a x86_64, with allmodconfig:
> Before:
> ======
>    text    data     bss     dec     hex filename
>   22403    4184      24   26611    67f3 fs/nilfs2/sysfs.o
>
> After:
> =====
>    text    data     bss     dec     hex filename
>   22723    3928      24   26675    6833 fs/nilfs2/sysfs.o
>
> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> ---
> Compile tested-only
> ---
>  fs/nilfs2/sysfs.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/fs/nilfs2/sysfs.c b/fs/nilfs2/sysfs.c
> index 379d22e28ed6..a5569b7f47a3 100644
> --- a/fs/nilfs2/sysfs.c
> +++ b/fs/nilfs2/sysfs.c
> @@ -56,7 +56,7 @@ static void nilfs_##name##_attr_release(struct kobject *kobj) \
>                                                 sg_##name##_kobj); \
>         complete(&subgroups->sg_##name##_kobj_unregister); \
>  } \
> -static struct kobj_type nilfs_##name##_ktype = { \
> +static const struct kobj_type nilfs_##name##_ktype = { \
>         .default_groups = nilfs_##name##_groups, \
>         .sysfs_ops      = &nilfs_##name##_attr_ops, \
>         .release        = nilfs_##name##_attr_release, \
> @@ -166,7 +166,7 @@ static const struct sysfs_ops nilfs_snapshot_attr_ops = {
>         .store  = nilfs_snapshot_attr_store,
>  };
>
> -static struct kobj_type nilfs_snapshot_ktype = {
> +static const struct kobj_type nilfs_snapshot_ktype = {
>         .default_groups = nilfs_snapshot_groups,
>         .sysfs_ops      = &nilfs_snapshot_attr_ops,
>         .release        = nilfs_snapshot_attr_release,
> @@ -967,7 +967,7 @@ static const struct sysfs_ops nilfs_dev_attr_ops = {
>         .store  = nilfs_dev_attr_store,
>  };
>
> -static struct kobj_type nilfs_dev_ktype = {
> +static const struct kobj_type nilfs_dev_ktype = {
>         .default_groups = nilfs_dev_groups,
>         .sysfs_ops      = &nilfs_dev_attr_ops,
>         .release        = nilfs_dev_attr_release,
> --
> 2.45.2
>

Thanks, this seems like a reasonable change.
I'll test it in a few environments just to be sure, and then send it upstream.

Ryusuke Konishi