From 48fddba63787167f7cdc718d39c99efedb0790f4 Mon Sep 17 00:00:00 2001
From: Mark Johnston <markj@FreeBSD.org>
Date: Thu, 20 Mar 2025 01:34:10 +0000
Subject: [PATCH] devfs: Return early from sysctl_devname() if no input is
 given

Otherwise we end up searching for a device using an uninitialized key,
tripping up KMSAN.

MFC after:	2 weeks

(cherry picked from commit 48d6b52add36cc09e7fb1fbec44ab66c0742f320)
---
 sys/fs/devfs/devfs_devs.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/sys/fs/devfs/devfs_devs.c b/sys/fs/devfs/devfs_devs.c
index db879efe803..c6dcd4fc764 100644
--- a/sys/fs/devfs/devfs_devs.c
+++ b/sys/fs/devfs/devfs_devs.c
@@ -86,6 +86,9 @@ sysctl_devname(SYSCTL_HANDLER_ARGS)
 	struct cdev_priv *cdp;
 	struct cdev *dev;
 
+	if (req->newptr == NULL)
+		return (EINVAL);
+
 #ifdef COMPAT_FREEBSD11
 	if (req->newlen == sizeof(ud_compat)) {
 		error = SYSCTL_IN(req, &ud_compat, sizeof(ud_compat));