Try this?

Author: alex

tests/chrdev/tests/tests.rs

@@ -1,13 +1,13 @@
-use std::ffi::CString;
 use std::io::Read;
 use std::path::PathBuf;
+use std::process::Command;
 use std::{env, fs};
 
 use libc;
 
 use kernel_module_testlib::with_kernel_module;
 
-fn get_device_number() -> libc::dev_t {
+fn get_device_major_number() -> libc::dev_t {
     let devices = fs::read_to_string("/proc/devices").unwrap();
     let dev_no_line = devices
         .lines()
@@ -31,31 +31,40 @@ struct UnlinkOnDrop<'a> {
 
 impl Drop for UnlinkOnDrop<'_> {
     fn drop(&mut self) {
-        fs::remove_file(self.path).unwrap();
+        Command::new("sudo")
+            .arg("rm")
+            .arg(self.path.to_str().unwrap())
+            .status()
+            .unwrap();
     }
 }
 
-fn mknod(path: &PathBuf, mode: u32, device_number: libc::dev_t) -> UnlinkOnDrop {
-    let path_cstr = CString::new(path.to_str().unwrap().as_bytes().to_vec()).unwrap();
-    let result = unsafe { libc::mknod(path_cstr.as_ptr(), mode, device_number) };
-    assert_eq!(result, 0);
+fn mknod(path: &PathBuf, device_number: libc::dev_t) -> UnlinkOnDrop {
+    Command::new("sudo")
+        .arg("mknod")
+        .arg(path.to_str().unwrap())
+        .arg("c")
+        .arg(device_number.to_string())
+        .arg("0")
+        .status()
+        .unwrap();
     return UnlinkOnDrop { path };
 }
 
 #[test]
 fn test_mknod() {
     with_kernel_module(|| {
-        let device_number = get_device_number();
-        mknod(&temporary_file_path(), 0o600, device_number);
+        let device_number = get_device_major_number();
+        mknod(&temporary_file_path(), device_number);
     });
 }
 
 #[test]
 fn test_read() {
     with_kernel_module(|| {
-        let device_number = get_device_number();
+        let device_number = get_device_major_number();
         let p = temporary_file_path();
-        let _u = mknod(&p, 0o600, device_number);
+        let _u = mknod(&p, device_number);
 
         let mut f = fs::File::open(&p).unwrap();
         let mut data = [0; 12];