[PATCH] sysctl: treewide: constify ctl_table_root::set_ownership

[Thomas Weißschuh <linux@xxxxxxxxxxxxxx>]

The set_ownership callback is not supposed to modify the ctl_table.
Enforce this expectation via the typesystem.

The patch was created with the following coccinelle script:

  virtual patch
  virtual context
  virtual report

  @@
  identifier func, head, table, uid, gid;
  @@

  void func(
    struct ctl_table_header *head,
  - struct ctl_table *table,
  + const struct ctl_table *table,
    kuid_t *uid, kgid_t *gid)
  { ... }

This change also is a step to put "struct ctl_table" into .rodata
throughout the kernel.

Signed-off-by: Thomas Weißschuh <linux@xxxxxxxxxxxxxx>
---
The patch is meant to be merged via the sysctl tree.

This change was originally part of the sysctl-const series [0].
To slim down that series and reduce the message load on other
maintainers to a minimumble, submit this patch on its own.

[0] https://lore.kernel.org/lkml/20231204-const-sysctl-v2-2-7a5060b11447@xxxxxxxxxxxxxx/
---
 include/linux/sysctl.h | 2 +-
 net/sysctl_net.c       | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 26a38161c28f..800154e1ff88 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -205,7 +205,7 @@ struct ctl_table_root {
 	struct ctl_table_set default_set;
 	struct ctl_table_set *(*lookup)(struct ctl_table_root *root);
 	void (*set_ownership)(struct ctl_table_header *head,
-			      struct ctl_table *table,
+			      const struct ctl_table *table,
 			      kuid_t *uid, kgid_t *gid);
 	int (*permissions)(struct ctl_table_header *head, struct ctl_table *table);
 };
diff --git a/net/sysctl_net.c b/net/sysctl_net.c
index 051ed5f6fc93..1310ef8f0958 100644
--- a/net/sysctl_net.c
+++ b/net/sysctl_net.c
@@ -54,7 +54,7 @@ static int net_ctl_permissions(struct ctl_table_header *head,
 }
 
 static void net_ctl_set_ownership(struct ctl_table_header *head,
-				  struct ctl_table *table,
+				  const struct ctl_table *table,
 				  kuid_t *uid, kgid_t *gid)
 {
 	struct net *net = container_of(head->set, struct net, sysctls);

---
base-commit: de2ee5e9405e12600c81e39837362800cee433a2
change-id: 20231226-sysctl-const-ownership-ff75e67b4eea

Best regards,
-- 
Thomas Weißschuh <linux@xxxxxxxxxxxxxx>