[utils] setproctitle: Fix NUL termination (#17724)

Authored by: doe1080

test/test_utils.py

@@ -107,6 +107,7 @@ from yt_dlp.utils import (
     sanitize_filename,
     sanitize_path,
     sanitize_url,
+    setproctitle,
     shell_quote,
     strftime_or_none,
     smuggle_url,
@@ -613,6 +614,14 @@ class TestUtil(unittest.TestCase):
         self.assertEqual(res_url, url)
         self.assertEqual(res_data, {'a': 'b', 'c': 'd'})
 
+    @unittest.mock.patch('ctypes.cdll.LoadLibrary')
+    def test_setproctitle(self, load_library):
+        for title in ('yt-dlp', 'café'):
+            with self.subTest(title=title):
+                setproctitle(title)
+                buf = load_library.return_value.prctl.call_args.args[1]
+                self.assertEqual(bytes(buf), title.encode() + b'\0')
+
     def test_shell_quote(self):
         args = ['ffmpeg', '-i', 'ñ€ß\'.mp4']
         self.assertEqual(

yt_dlp/utils/_utils.py

@@ -1959,9 +1959,7 @@ def setproctitle(title):
     except OSError:
         return
 
-    title_bytes = title.encode()
-    buf = ctypes.create_string_buffer(len(title_bytes))
-    buf.value = title_bytes
+    buf = ctypes.create_string_buffer(title.encode())
     try:
         # PR_SET_NAME = 15      Ref: /usr/include/linux/prctl.h
         libc.prctl(15, buf, 0, 0, 0)