linux-kernel - [PATCH 3/5] sysctl: allow registration of const struct ctl

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Message-Id: <20240729-sysctl-const-api-v1-3-ca628c7a942c@weissschuh.net>
Date: Mon, 29 Jul 2024 22:43:32 +0200
From: Thomas Weißschuh <linux@...ssschuh.net>
To: Alexei Starovoitov <ast@...nel.org>, 
 Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, 
 Martin KaFai Lau <martin.lau@...ux.dev>, 
 Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
 Yonghong Song <yonghong.song@...ux.dev>, 
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>, 
 Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, 
 Jiri Olsa <jolsa@...nel.org>, Luis Chamberlain <mcgrof@...nel.org>, 
 Kees Cook <kees@...nel.org>, Joel Granados <j.granados@...sung.com>
Cc: bpf@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-fsdevel@...r.kernel.org, 
 Thomas Weißschuh <linux@...ssschuh.net>
Subject: [PATCH 3/5] sysctl: allow registration of const struct ctl_table

Putting structure, especially those containing function pointers,
into read-only memory makes the safer and easier to reason about.
Change the sysctl registration APIs to allow registration of
"const struct ctl_table".

Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
---
 fs/proc/proc_sysctl.c  |  6 +++---
 include/linux/sysctl.h | 10 +++++-----
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index fa8cf9bf2988..01e006cc1163 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -1354,7 +1354,7 @@ static struct ctl_dir *sysctl_mkdir_p(struct ctl_dir *dir, const char *path)
  */
 struct ctl_table_header *__register_sysctl_table(
 	struct ctl_table_set *set,
-	const char *path, struct ctl_table *table, size_t table_size)
+	const char *path, const struct ctl_table *table, size_t table_size)
 {
 	struct ctl_table_root *root = set->dir.header.root;
 	struct ctl_table_header *header;
@@ -1415,7 +1415,7 @@ struct ctl_table_header *__register_sysctl_table(
  *
  * See __register_sysctl_table for more details.
  */
-struct ctl_table_header *register_sysctl_sz(const char *path, struct ctl_table *table,
+struct ctl_table_header *register_sysctl_sz(const char *path, const struct ctl_table *table,
 					    size_t table_size)
 {
 	return __register_sysctl_table(&sysctl_table_root.default_set,
@@ -1444,7 +1444,7 @@ EXPORT_SYMBOL(register_sysctl_sz);
  *
  * Context: if your base directory does not exist it will be created for you.
  */
-void __init __register_sysctl_init(const char *path, struct ctl_table *table,
+void __init __register_sysctl_init(const char *path, const struct ctl_table *table,
 				 const char *table_name, size_t table_size)
 {
 	struct ctl_table_header *hdr = register_sysctl_sz(path, table, table_size);
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index a473deaf5a91..202855befa8b 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -223,13 +223,13 @@ extern void retire_sysctl_set(struct ctl_table_set *set);
 
 struct ctl_table_header *__register_sysctl_table(
 	struct ctl_table_set *set,
-	const char *path, struct ctl_table *table, size_t table_size);
-struct ctl_table_header *register_sysctl_sz(const char *path, struct ctl_table *table,
+	const char *path, const struct ctl_table *table, size_t table_size);
+struct ctl_table_header *register_sysctl_sz(const char *path, const struct ctl_table *table,
 					    size_t table_size);
 void unregister_sysctl_table(struct ctl_table_header * table);
 
 extern int sysctl_init_bases(void);
-extern void __register_sysctl_init(const char *path, struct ctl_table *table,
+extern void __register_sysctl_init(const char *path, const struct ctl_table *table,
 				 const char *table_name, size_t table_size);
 #define register_sysctl_init(path, table)	\
 	__register_sysctl_init(path, table, #table, ARRAY_SIZE(table))
@@ -251,7 +251,7 @@ extern int no_unaligned_warning;
 
 #else /* CONFIG_SYSCTL */
 
-static inline void register_sysctl_init(const char *path, struct ctl_table *table)
+static inline void register_sysctl_init(const char *path, const struct ctl_table *table)
 {
 }
 
@@ -261,7 +261,7 @@ static inline struct ctl_table_header *register_sysctl_mount_point(const char *p
 }
 
 static inline struct ctl_table_header *register_sysctl_sz(const char *path,
-							  struct ctl_table *table,
+							  const struct ctl_table *table,
 							  size_t table_size)
 {
 	return NULL;

-- 
2.45.2