[PATCH] syscall_user_dispatch: Use CONFIG_SYSCTL for sysctl guard

[PATCH] syscall_user_dispatch: Use CONFIG_SYSCTL for sysctl guard

[Karl Mehltretter]

sysctl-next removes CONFIG_PROC_SYSCTL because it mirrors CONFIG_SYSCTL.
When combined with the syscall user dispatch sysctl in linux-next, the
stale guard prevents registration of kernel.syscall_user_dispatch.

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
Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
---
The conflicting sysctl-next commit is currently:

  8d75c338f0bc ("sysctl: remove CONFIG_PROC_SYSCTL, it just mirrors CONFIG_SYSCTL")

This is a cross-tree integration fix intended for the tip tree. It has
no functional effect in tip/master, but restores the sysctl when
combined with sysctl-next.

Verified in linux-next with an x86_64 object build using
CONFIG_SYSCALL_USER_DISPATCH=y and CONFIG_SYSCTL=y.

 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 b6328cd0f43e9..ffea61d448ebb 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 2002c7aae4358..59c861866941d 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: 98292902c7108717c4f4bea7226520b336f9a8bc
-- 
2.53.0

Re: [PATCH] syscall_user_dispatch: Use CONFIG_SYSCTL for sysctl guard

[Oleg Nesterov]

On 08/13, Karl Mehltretter wrote:
>
> --- 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 */

Thanks!

Acked-by: Oleg Nesterov <oleg@redhat.com>


and just in case... this change is fine even without
8d75c338f0bc ("sysctl: remove CONFIG_PROC_SYSCTL, it just mirrors CONFIG_SYSCTL")
from sysctl-next.

Oleg.