kobject: Replace strlcpy with strscpy

strlcpy() reads the entire source buffer first.
This read may exceed the destination size limit.
This is both inefficient and can lead to linear read
overflows if a source string is not NUL-terminated [1].
In an effort to remove strlcpy() completely [2], replace
strlcpy() here with strscpy().

Direct replacement is safe here since return value of -errno
is used to check for truncation instead of sizeof(dest).

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
[2] KSPP#89

Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20230831140104.207019-1-azeemshaikh38@gmail.com
Signed-off-by: Kees Cook <keescook@chromium.org>

Author: azeemshaikh38

lib/kobject_uevent.c

@@ -254,10 +254,10 @@ static int init_uevent_argv(struct kobj_uevent_env *env, const char *subsystem)
 	int buffer_size = sizeof(env->buf) - env->buflen;
 	int len;
 
-	len = strlcpy(&env->buf[env->buflen], subsystem, buffer_size);
-	if (len >= buffer_size) {
-		pr_warn("init_uevent_argv: buffer size of %d too small, needed %d\n",
-			buffer_size, len);
+	len = strscpy(&env->buf[env->buflen], subsystem, buffer_size);
+	if (len < 0) {
+		pr_warn("%s: insufficient buffer space (%u left) for %s\n",
+			__func__, buffer_size, subsystem);
 		return -ENOMEM;
 	}