From b9817d714c372df86dea9b924c4a712872b0bf4e Mon Sep 17 00:00:00 2001
From: AN Long <aisk1988@gmail.com>
Date: Fri, 20 Mar 2026 20:45:41 +0800
Subject: [PATCH 1/2] Check the errno with != 0 in close impls

---
 Lib/test/test_devpoll.py | 10 ++++++++++
 Lib/test/test_epoll.py   |  9 +++++++++
 Lib/test/test_kqueue.py  |  9 +++++++++
 Modules/selectmodule.c   | 15 +++++++++------
 4 files changed, 37 insertions(+), 6 deletions(-)

diff --git a/Lib/test/test_devpoll.py b/Lib/test/test_devpoll.py
index 85e0accb611b1d..5951f8817ab1c1 100644
--- a/Lib/test/test_devpoll.py
+++ b/Lib/test/test_devpoll.py
@@ -2,6 +2,7 @@
 
 # Initial tests are copied as is from "test_poll.py"
 
+import errno
 import os
 import random
 import select
@@ -112,6 +113,15 @@ def test_close(self):
         self.assertRaises(ValueError, devpoll.register, fd, select.POLLIN)
         self.assertRaises(ValueError, devpoll.unregister, fd)
 
+    def test_close_error(self):
+        # gh-146205: close() should raise OSError if underlying fd is invalid
+        devpoll = select.devpoll()
+        fd = devpoll.fileno()
+        os.close(fd)
+        with self.assertRaises(OSError) as cm:
+            devpoll.close()
+        self.assertEqual(cm.exception.errno, errno.EBADF)
+
     def test_fd_non_inheritable(self):
         devpoll = select.devpoll()
         self.addCleanup(devpoll.close)
diff --git a/Lib/test/test_epoll.py b/Lib/test/test_epoll.py
index c94946a6ae6b7c..5e6a4ab0166a86 100644
--- a/Lib/test/test_epoll.py
+++ b/Lib/test/test_epoll.py
@@ -259,6 +259,15 @@ def test_close(self):
         self.assertRaises(ValueError, epoll.register, fd, select.EPOLLIN)
         self.assertRaises(ValueError, epoll.unregister, fd)
 
+    def test_close_error(self):
+        # gh-146205: close() should raise OSError if underlying fd is invalid
+        epoll = select.epoll()
+        fd = epoll.fileno()
+        os.close(fd)
+        with self.assertRaises(OSError) as cm:
+            epoll.close()
+        self.assertEqual(cm.exception.errno, errno.EBADF)
+
     def test_fd_non_inheritable(self):
         epoll = select.epoll()
         self.addCleanup(epoll.close)
diff --git a/Lib/test/test_kqueue.py b/Lib/test/test_kqueue.py
index d2ab45c4a5b1ea..2cf99be9e2c3ba 100644
--- a/Lib/test/test_kqueue.py
+++ b/Lib/test/test_kqueue.py
@@ -254,6 +254,15 @@ def test_close(self):
         # operations must fail with ValueError("I/O operation on closed ...")
         self.assertRaises(ValueError, kqueue.control, None, 4)
 
+    def test_close_error(self):
+        # gh-146205: close() should raise OSError if underlying fd is invalid
+        kqueue = select.kqueue()
+        fd = kqueue.fileno()
+        os.close(fd)
+        with self.assertRaises(OSError) as cm:
+            kqueue.close()
+        self.assertEqual(cm.exception.errno, errno.EBADF)
+
     def test_fd_non_inheritable(self):
         kqueue = select.kqueue()
         self.addCleanup(kqueue.close)
diff --git a/Modules/selectmodule.c b/Modules/selectmodule.c
index 137bf2ca55bbf8..4dd544c6ee8d34 100644
--- a/Modules/selectmodule.c
+++ b/Modules/selectmodule.c
@@ -1118,8 +1118,9 @@ static PyObject *
 select_devpoll_close_impl(devpollObject *self)
 /*[clinic end generated code: output=26b355bd6429f21b input=408fde21a377ccfb]*/
 {
-    errno = devpoll_internal_close(self);
-    if (errno < 0) {
+    int err = devpoll_internal_close(self);
+    if (err != 0) {
+        errno = err;
         PyErr_SetFromErrno(PyExc_OSError);
         return NULL;
     }
@@ -1446,8 +1447,9 @@ static PyObject *
 select_epoll_close_impl(pyEpoll_Object *self)
 /*[clinic end generated code: output=ee2144c446a1a435 input=f626a769192e1dbe]*/
 {
-    errno = pyepoll_internal_close(self);
-    if (errno < 0) {
+    int err = pyepoll_internal_close(self);
+    if (err != 0) {
+        errno = err;
         PyErr_SetFromErrno(PyExc_OSError);
         return NULL;
     }
@@ -2263,8 +2265,9 @@ static PyObject *
 select_kqueue_close_impl(kqueue_queue_Object *self)
 /*[clinic end generated code: output=d1c7df0b407a4bc1 input=6d763c858b17b690]*/
 {
-    errno = kqueue_queue_internal_close(self);
-    if (errno < 0) {
+    int err = kqueue_queue_internal_close(self);
+    if (err != 0) {
+        errno = err;
         PyErr_SetFromErrno(PyExc_OSError);
         return NULL;
     }

From 53d6b3a3361091bb5aaf5ce57513b14a00d5a4bf Mon Sep 17 00:00:00 2001
From: "blurb-it[bot]" <43283697+blurb-it[bot]@users.noreply.github.com>
Date: Fri, 20 Mar 2026 12:53:05 +0000
Subject: [PATCH 2/2] =?UTF-8?q?=F0=9F=93=9C=F0=9F=A4=96=20Added=20by=20blu?=
 =?UTF-8?q?rb=5Fit.?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../2026-03-20-12-52-55.gh-issue-146205.M4yKdf.rst              | 2 ++
 1 file changed, 2 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Core_and_Builtins/2026-03-20-12-52-55.gh-issue-146205.M4yKdf.rst

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-03-20-12-52-55.gh-issue-146205.M4yKdf.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-03-20-12-52-55.gh-issue-146205.M4yKdf.rst
new file mode 100644
index 00000000000000..e9d95cdf836dba
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2026-03-20-12-52-55.gh-issue-146205.M4yKdf.rst
@@ -0,0 +1,2 @@
+Fixed a bug where :meth:`select.epoll.close`, :meth:`select.kqueue.close`,
+and :meth:`select.devpoll.close` silently ignored errors.