[PATCH v2] syscall_user_dispatch: Use CONFIG_SYSCTL for sysctl guard

[Karl Mehltretter <kmehltretter@gmail.com>]

Commit 8d75c338f0bc ("sysctl: remove CONFIG_PROC_SYSCTL, it just mirrors
CONFIG_SYSCTL") removed CONFIG_PROC_SYSCTL, but the sysctl added by
commit 5b6e32ba7b59 ("syscall_user_dispatch: Add
kernel.syscall_user_dispatch sysctl") is still guarded by it. Now that
both commits are merged, kernel.syscall_user_dispatch is no longer
registered.

syscall_user_dispatch_allowed defaults to true. SUD therefore remains
available, but administrators cannot disable new activations.

Use CONFIG_SYSCTL for the guard and documentation.

Fixes: 5b6e32ba7b59 ("syscall_user_dispatch: Add kernel.syscall_user_dispatch sysctl")
Assisted-by: Codex:gpt-5.6-sol
Acked-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Joel Granados <joel.granados@kernel.org>
Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
---
Changes in v2:
  - Reword changelog and rebase onto mainline now that both commits
    are merged there (v7.2 is unaffected, it has neither commit).
  - Collected Acked-by/Reviewed-by tags from v1. No code change.

v1: https://lore.kernel.org/all/20260813062039.14567-1-kmehltretter@gmail.com/

 Documentation/admin-guide/sysctl/kernel.rst | 2 +-
 kernel/entry/syscall_user_dispatch.c        | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
index b6328cd0f43e..ffea61d448eb 100644
--- a/Documentation/admin-guide/sysctl/kernel.rst
+++ b/Documentation/admin-guide/sysctl/kernel.rst
@@ -1416,7 +1416,7 @@ Controls whether userspace may arm Syscall User Dispatch via
   ==  ===================================================================
 
 Only present when the kernel is built with ``CONFIG_SYSCALL_USER_DISPATCH``
-and ``CONFIG_PROC_SYSCTL``.
+and ``CONFIG_SYSCTL``.
 
 
 sysctl_writes_strict
diff --git a/kernel/entry/syscall_user_dispatch.c b/kernel/entry/syscall_user_dispatch.c
index 2002c7aae435..59c861866941 100644
--- a/kernel/entry/syscall_user_dispatch.c
+++ b/kernel/entry/syscall_user_dispatch.c
@@ -178,7 +178,7 @@ int syscall_user_dispatch_set_config(struct task_struct *task, unsigned long siz
 					      (char __user *)(uintptr_t)cfg.selector);
 }
 
-#ifdef CONFIG_PROC_SYSCTL
+#ifdef CONFIG_SYSCTL
 static const struct ctl_table syscall_user_dispatch_sysctls[] = {
 	{
 		.procname	= "syscall_user_dispatch",
@@ -195,4 +195,4 @@ static int __init syscall_user_dispatch_sysctl_init(void)
 	return 0;
 }
 late_initcall(syscall_user_dispatch_sysctl_init);
-#endif /* CONFIG_PROC_SYSCTL */
+#endif /* CONFIG_SYSCTL */

base-commit: 26260251022fbc2f248a3d747a9b2b961b18d2d8
-- 
2.39.5 (Apple Git-154)