Issue python#29335: Fix subprocess.Popen.wait() when the child process has

exited to a stopped instead of terminated state (ex: when under ptrace).

Author: gpshead

Lib/subprocess.py

@@ -1285,14 +1285,17 @@ def _execute_child(self, args, executable, preexec_fn, close_fds,
 
         def _handle_exitstatus(self, sts, _WIFSIGNALED=os.WIFSIGNALED,
                 _WTERMSIG=os.WTERMSIG, _WIFEXITED=os.WIFEXITED,
-                _WEXITSTATUS=os.WEXITSTATUS):
+                _WEXITSTATUS=os.WEXITSTATUS, _WIFSTOPPED=os.WIFSTOPPED,
+                _WSTOPSIG=os.WSTOPSIG):
             """All callers to this function MUST hold self._waitpid_lock."""
             # This method is called (indirectly) by __del__, so it cannot
             # refer to anything outside of its local scope.
             if _WIFSIGNALED(sts):
                 self.returncode = -_WTERMSIG(sts)
             elif _WIFEXITED(sts):
                 self.returncode = _WEXITSTATUS(sts)
+            elif _WIFSTOPPED(sts):
+                self.returncode = -_WSTOPSIG(sts)
             else:
                 # Should never happen
                 raise SubprocessError("Unknown child exit status!")

Lib/test/test_subprocess.py

@@ -4,6 +4,8 @@
 from test import support
 import subprocess
 import sys
+import platform
+import ctypes
 import signal
 import io
 import locale
@@ -2448,6 +2450,45 @@ def test_communicate_BrokenPipeError_stdin_close_with_timeout(self):
             proc.communicate(timeout=999)
             mock_proc_stdin.close.assert_called_once_with()
 
+    _libc_file_extensions = {
+      'Linux': 'so.6',
+      'Darwin': '.dylib',
+    }
+    @unittest.skipIf(platform.uname()[0] not in _libc_file_extensions,
+                     'Test requires a libc this code can load with ctypes.')
+    @unittest.skipIf(not sys.executable, 'Test requires sys.executable.')
+    def test_child_terminated_in_stopped_state(self):
+        """Test wait() behavior when waitpid returns WIFSTOPPED; issue29335."""
+        PTRACE_TRACEME = 0  # From glibc and MacOS (PT_TRACE_ME).
+        libc_name = 'libc.' + self._libc_file_extensions[platform.uname()[0]]
+        libc = ctypes.CDLL(libc_name)
+        if not hasattr(libc, 'ptrace'):
+            raise unittest.SkipTest('ptrace() required.')
+        test_ptrace = subprocess.Popen(
+            [sys.executable, '-c', """if True:
+             import ctypes
+             libc = ctypes.CDLL({libc_name!r})
+             libc.ptrace({PTRACE_TRACEME}, 0, 0)
+             """.format(libc_name=libc_name, PTRACE_TRACEME=PTRACE_TRACEME)
+            ])
+        if test_ptrace.wait() != 0:
+            raise unittest.SkipTest('ptrace() failed - unable to test.')
+        child = subprocess.Popen(
+            [sys.executable, '-c', """if True:
+             import ctypes
+             libc = ctypes.CDLL({libc_name!r})
+             libc.ptrace({PTRACE_TRACEME}, 0, 0)
+             libc.printf(ctypes.c_char_p(0xdeadbeef))  # Crash the process.
+             """.format(libc_name=libc_name, PTRACE_TRACEME=PTRACE_TRACEME)
+            ])
+        try:
+            returncode = child.wait()
+        except Exception as e:
+            child.kill()  # Clean up the hung stopped process.
+            raise e
+        self.assertNotEqual(0, returncode)
+        self.assertLess(returncode, 0)  # signal death, likely SIGSEGV.
+
 
 @unittest.skipUnless(mswindows, "Windows specific tests")
 class Win32ProcessTestCase(BaseTestCase):

Misc/NEWS

@@ -13,6 +13,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #29335: Fix subprocess.Popen.wait() when the child process has
+  exited to a stopped instead of terminated state (ex: when under ptrace).
+
 - Issue #29290: Fix a regression in argparse that help messages would wrap at
   non-breaking spaces.