Re: [PATCH] add utsname_set_field to reuse code in setdomainname and sethostname

[Bradley Morgan <bradley.morgan@linux.dev>]

On 11 November 2026 07:33:17 GMT, Laurijssen <lauserve@gmail.com> wrote:
>Changes after review, cleanup of duplicated code in sethostname and
>setdomainname.
>
>- add static utsname_set_field sys.c
>- call utsname_set_field from sethostname/setdomainname
>- code compiles now when CONFIG_SYSCTL is not defined

This changelog seriously isn't great, like this description is absolutely
unmergable. Please read docs.

NAK.

>
>Signed-off-by: Laurijssen <laurijssen@protonmail.com>
>---
> kernel/sys.c | 53 ++++++++++++++++++++++++++--------------------------
> 1 file changed, 27 insertions(+), 26 deletions(-)
>
>diff --git a/kernel/sys.c b/kernel/sys.c
>index 755bfa5ccd92..77fedd127a3f 100644
>--- a/kernel/sys.c
>+++ b/kernel/sys.c
>@@ -1419,7 +1419,7 @@ SYSCALL_DEFINE1(olduname, struct oldold_utsname __user *, name)
> }
> #endif
> 
>-SYSCALL_DEFINE2(sethostname, char __user *, name, int, len)
>+static int utsname_set_field(char __user *name, int len, enum uts_proc proc)
> {
> 	int errno;
> 	char tmp[__NEW_UTS_LEN];
>@@ -1432,19 +1432,41 @@ SYSCALL_DEFINE2(sethostname, char __user *, name, int, len)
> 	errno = -EFAULT;
> 	if (!copy_from_user(tmp, name, len)) {
> 		struct new_utsname *u;
>+		char *field;
> 
> 		add_device_randomness(tmp, len);
> 		down_write(&uts_sem);
>+
> 		u = utsname();
>-		memcpy(u->nodename, tmp, len);
>-		memset(u->nodename + len, 0, sizeof(u->nodename) - len);
>+
>+		switch (proc) {
>+		case UTS_PROC_HOSTNAME:
>+			field = u->nodename;
>+			break;
>+		case UTS_PROC_DOMAINNAME:
>+			field = u->domainname;
>+			break;
>+		default:
>+			WARN_ON_ONCE(1);
>+			field = u->domainname;
>+			break;
>+		}
>+
>+		memcpy(field, tmp, len);
>+		memset(field + len, 0, sizeof_field(struct new_utsname, nodename) - len);
>+
> 		errno = 0;
>-		uts_proc_notify(UTS_PROC_HOSTNAME);
>+		uts_proc_notify(proc);
> 		up_write(&uts_sem);
> 	}
> 	return errno;
> }
> 
>+SYSCALL_DEFINE2(sethostname, char __user *, name, int, len)
>+{
>+	return utsname_set_field(name, len, UTS_PROC_HOSTNAME);
>+}
>+
> #ifdef __ARCH_WANT_SYS_GETHOSTNAME
> 
> SYSCALL_DEFINE2(gethostname, char __user *, name, int, len)
>@@ -1475,28 +1497,7 @@ SYSCALL_DEFINE2(gethostname, char __user *, name, int, len)
>  */
> SYSCALL_DEFINE2(setdomainname, char __user *, name, int, len)
> {
>-	int errno;
>-	char tmp[__NEW_UTS_LEN];
>-
>-	if (!ns_capable(current->nsproxy->uts_ns->user_ns, CAP_SYS_ADMIN))
>-		return -EPERM;
>-	if (len < 0 || len > __NEW_UTS_LEN)
>-		return -EINVAL;
>-
>-	errno = -EFAULT;
>-	if (!copy_from_user(tmp, name, len)) {
>-		struct new_utsname *u;
>-
>-		add_device_randomness(tmp, len);
>-		down_write(&uts_sem);
>-		u = utsname();
>-		memcpy(u->domainname, tmp, len);
>-		memset(u->domainname + len, 0, sizeof(u->domainname) - len);
>-		errno = 0;
>-		uts_proc_notify(UTS_PROC_DOMAINNAME);
>-		up_write(&uts_sem);
>-	}
>-	return errno;
>+	return utsname_set_field(name, len, UTS_PROC_DOMAINNAME);
> }
> 
> /* make sure you are allowed to change @tsk limits before calling this */
>

--- Thanks!