Fix issue #6973: When we know a subprocess.Popen process has died, do

not allow the send_signal(), terminate(), or kill() methods to do
anything as they could potentially signal a different process.

1 files changed, 12 insertions, 7 deletions

diff --git a/Lib/subprocess.py b/Lib/subprocess.py
index b6c437438e..bbf50ce760 100644
--- a/Lib/subprocess.py
+++ b/Lib/subprocess.py
@@ -1333,8 +1333,10 @@ class Popen(object):
             return (stdout, stderr)
 
         def send_signal(self, sig):
-            """Send a signal to the process
-            """
+            """Send a signal to the process."""
+            # Don't signal a process that we know has already died.
+            if self.returncode is not None:
+                return
             if sig == signal.SIGTERM:
                 self.terminate()
             elif sig == signal.CTRL_C_EVENT:
@@ -1345,8 +1347,10 @@ class Popen(object):
                 raise ValueError("Unsupported signal: {}".format(sig))
 
         def terminate(self):
-            """Terminates the process
-            """
+            """Terminates the process."""
+            # Don't terminate a process that we know has already died.
+            if self.returncode is not None:
+                return
             try:
                 _winapi.TerminateProcess(self._handle, 1)
             except PermissionError:
@@ -1754,9 +1758,10 @@ class Popen(object):
 
 
         def send_signal(self, sig):
-            """Send a signal to the process
-            """
-            os.kill(self.pid, sig)
+            """Send a signal to the process."""
+            # Skip signalling a process that we know has already died.
+            if self.returncode is None:
+                os.kill(self.pid, sig)
 
         def terminate(self):
             """Terminate the process with SIGTERM