commit 5654f83b9706af88040f515791f1cdc5d81cd9d6
author Alex Rebert <alex@forallsecure.com> Thu Jan 23 18:31:29 2020 -0500
committer Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com> Thu Jan 23 15:31:29 2020 -0800
tree e433c05b39908f19fcdc3a1a00c1fb8e5e1cde93
parent 5a2356be1a3f4a9b2e509a16062016b7d9dee7e9

[3.8] bpo-35182: fix communicate() crash after child closes its pipes (GH-18117) (GH-18148)



When communicate() is called in a loop, it crashes when the child process
has already closed any piped standard stream, but still continues to be running

Co-authored-by: Andriy Maletsky <andriy.maletsky@gmail.com>.
(cherry picked from commit d3ae95e1e945ed20297e1c38ba43a18b7a868ab6)

Co-authored-by: Alex Rebert <alex@forallsecure.com>





https://bugs.python.org/issue35182

Lib/subprocess.py

diff --git a/Lib/subprocess.py b/Lib/subprocess.py
index 85b9ea0..5c2c2f0 100644
--- a/Lib/subprocess.py
+++ b/Lib/subprocess.py
@@ -1848,9 +1848,9 @@
             with _PopenSelector() as selector:
                 if self.stdin and input:
                     selector.register(self.stdin, selectors.EVENT_WRITE)
-                if self.stdout:
+                if self.stdout and not self.stdout.closed:
                     selector.register(self.stdout, selectors.EVENT_READ)
-                if self.stderr:
+                if self.stderr and not self.stderr.closed:
                     selector.register(self.stderr, selectors.EVENT_READ)
 
                 while selector.get_map():