[Python-checkins] gh-96819: multiprocessing.resource_tracker: check if length of pipe write <= 512 (GH-96890)

[miss-islington]

https://github.com/python/cpython/commit/c2d3f73da780ce4d568f541fb7f55917a814d65c
commit: c2d3f73da780ce4d568f541fb7f55917a814d65c
branch: 3.10
author: Miss Islington (bot) <31488909+miss-islington at users.noreply.github.com>
committer: miss-islington <31488909+miss-islington at users.noreply.github.com>
date: 2022-10-02T18:11:17-07:00
summary:

gh-96819: multiprocessing.resource_tracker: check if length of pipe write <= 512 (GH-96890)


Co-authored-by: Kumar Aditya <59607654+kumaraditya303 at users.noreply.github.com>
(cherry picked from commit 19ca114645bd8796cf4094e152b1fa9944da473d)

Co-authored-by: Koki Saito <49419225+saito828koki at users.noreply.github.com>

files:
A Misc/NEWS.d/next/Library/2022-09-17-13-15-10.gh-issue-96819.6RfqM7.rst
M Lib/multiprocessing/resource_tracker.py
M Lib/test/_test_multiprocessing.py

diff --git a/Lib/multiprocessing/resource_tracker.py b/Lib/multiprocessing/resource_tracker.py
index cc42dbdda05b..ea369507297f 100644
--- a/Lib/multiprocessing/resource_tracker.py
+++ b/Lib/multiprocessing/resource_tracker.py
@@ -161,10 +161,10 @@ def unregister(self, name, rtype):
     def _send(self, cmd, name, rtype):
         self.ensure_running()
         msg = '{0}:{1}:{2}\n'.format(cmd, name, rtype).encode('ascii')
-        if len(name) > 512:
+        if len(msg) > 512:
             # posix guarantees that writes to a pipe of less than PIPE_BUF
             # bytes are atomic, and that PIPE_BUF >= 512
-            raise ValueError('name too long')
+            raise ValueError('msg too long')
         nbytes = os.write(self._fd, msg)
         assert nbytes == len(msg), "nbytes {0:n} but len(msg) {1:n}".format(
             nbytes, len(msg))
diff --git a/Lib/test/_test_multiprocessing.py b/Lib/test/_test_multiprocessing.py
index 8dced90c5383..be174aae3d63 100644
--- a/Lib/test/_test_multiprocessing.py
+++ b/Lib/test/_test_multiprocessing.py
@@ -5377,6 +5377,14 @@ def test_resource_tracker_reused(self):
 
         self.assertTrue(is_resource_tracker_reused)
 
+    def test_too_long_name_resource(self):
+        # gh-96819: Resource names that will make the length of a write to a pipe
+        # greater than PIPE_BUF are not allowed
+        rtype = "shared_memory"
+        too_long_name_resource = "a" * (512 - len(rtype))
+        with self.assertRaises(ValueError):
+            resource_tracker.register(too_long_name_resource, rtype)
+
 
 class TestSimpleQueue(unittest.TestCase):
 
diff --git a/Misc/NEWS.d/next/Library/2022-09-17-13-15-10.gh-issue-96819.6RfqM7.rst b/Misc/NEWS.d/next/Library/2022-09-17-13-15-10.gh-issue-96819.6RfqM7.rst
new file mode 100644
index 000000000000..07b62a883b85
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2022-09-17-13-15-10.gh-issue-96819.6RfqM7.rst
@@ -0,0 +1 @@
+Fixed check in :mod:`multiprocessing.resource_tracker` that guarantees that the length of a write to a pipe is not greater than ``PIPE_BUF``.