From 18b8a71dcd67f0c01541968023c6a53f3e5e0d11 Mon Sep 17 00:00:00 2001
From: cptpcrd <31829097+cptpcrd@users.noreply.github.com>
Date: Fri, 8 Jan 2021 15:46:11 -0500
Subject: [PATCH 1/3] bpo-42780: fix set_inheritable() for O_PATH file
 descriptors on Linux

---
 Lib/test/test_os.py                           | 21 +++++++++++++++++++
 .../2021-01-08-15-49-20.bpo-42780.rtqi6B.rst  |  1 +
 Python/fileutils.c                            |  7 +++++++
 3 files changed, 29 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Library/2021-01-08-15-49-20.bpo-42780.rtqi6B.rst

diff --git a/Lib/test/test_os.py b/Lib/test/test_os.py
index 08d7ab8a30ba7e..e41ea2ea012951 100644
--- a/Lib/test/test_os.py
+++ b/Lib/test/test_os.py
@@ -3881,6 +3881,27 @@ def test_set_inheritable_cloexec(self):
         self.assertEqual(fcntl.fcntl(fd, fcntl.F_GETFD) & fcntl.FD_CLOEXEC,
                          0)
 
+    @unittest.skipUnless(hasattr(os, 'O_PATH'), "need os.O_PATH")
+    def test_get_set_inheritable_o_path(self):
+        fd = os.open(__file__, os.O_PATH)
+        self.addCleanup(os.close, fd)
+        self.assertEqual(os.get_inheritable(fd), False)
+
+        os.set_inheritable(fd, True)
+        self.assertEqual(os.get_inheritable(fd), True)
+
+        os.set_inheritable(fd, False)
+        self.assertEqual(os.get_inheritable(fd), False)
+
+    def test_get_set_inheritable_badf(self):
+        with self.assertRaises(OSError) as ctx:
+            os.set_inheritable(-1, True)
+        self.assertEqual(ctx.exception.errno, errno.EBADF)
+
+        with self.assertRaises(OSError) as ctx:
+            os.set_inheritable(-1, False)
+        self.assertEqual(ctx.exception.errno, errno.EBADF)
+
     def test_open(self):
         fd = os.open(__file__, os.O_RDONLY)
         self.addCleanup(os.close, fd)
diff --git a/Misc/NEWS.d/next/Library/2021-01-08-15-49-20.bpo-42780.rtqi6B.rst b/Misc/NEWS.d/next/Library/2021-01-08-15-49-20.bpo-42780.rtqi6B.rst
new file mode 100644
index 00000000000000..a491690507129e
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2021-01-08-15-49-20.bpo-42780.rtqi6B.rst
@@ -0,0 +1 @@
+Fix os.set_inheritable() for O_PATH file descriptors on Linux.
diff --git a/Python/fileutils.c b/Python/fileutils.c
index 8dc90fbe2b2e71..f2b4681ea849c5 100644
--- a/Python/fileutils.c
+++ b/Python/fileutils.c
@@ -1234,6 +1234,13 @@ set_inheritable(int fd, int inheritable, int raise, int *atomic_flag_works)
             return 0;
         }
 
+#ifdef __linux__
+        if (errno == EBADF) {
+            // On Linux, ioctl(FIOCLEX) will fail with EBADF for O_PATH file descriptors
+            // Fall through to the fcntl() path
+        }
+        else
+#endif
         if (errno != ENOTTY && errno != EACCES) {
             if (raise)
                 PyErr_SetFromErrno(PyExc_OSError);

From 24034fbbf49b24ff3b46d681eb7991144886c43d Mon Sep 17 00:00:00 2001
From: cptpcrd <31829097+cptpcrd@users.noreply.github.com>
Date: Wed, 20 Jan 2021 08:13:39 -0500
Subject: [PATCH 2/3] bpo-42780: use os_helper.make_bad_fd() in "inheritable"
 test

---
 Lib/test/test_os.py | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/Lib/test/test_os.py b/Lib/test/test_os.py
index e41ea2ea012951..4276987ffb5796 100644
--- a/Lib/test/test_os.py
+++ b/Lib/test/test_os.py
@@ -3894,12 +3894,14 @@ def test_get_set_inheritable_o_path(self):
         self.assertEqual(os.get_inheritable(fd), False)
 
     def test_get_set_inheritable_badf(self):
+        fd = os_helper.make_bad_fd()
+
         with self.assertRaises(OSError) as ctx:
-            os.set_inheritable(-1, True)
+            os.set_inheritable(fd, True)
         self.assertEqual(ctx.exception.errno, errno.EBADF)
 
         with self.assertRaises(OSError) as ctx:
-            os.set_inheritable(-1, False)
+            os.set_inheritable(fd, False)
         self.assertEqual(ctx.exception.errno, errno.EBADF)
 
     def test_open(self):

From 731ee777fc80612a9084ba8291baba9ee8432bd0 Mon Sep 17 00:00:00 2001
From: cptpcrd <31829097+cptpcrd@users.noreply.github.com>
Date: Wed, 20 Jan 2021 08:15:07 -0500
Subject: [PATCH 3/3] bpo-42780: test for EBADF from os.get_inheritable()

---
 Lib/test/test_os.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Lib/test/test_os.py b/Lib/test/test_os.py
index 4276987ffb5796..96fddc7d057663 100644
--- a/Lib/test/test_os.py
+++ b/Lib/test/test_os.py
@@ -3896,6 +3896,10 @@ def test_get_set_inheritable_o_path(self):
     def test_get_set_inheritable_badf(self):
         fd = os_helper.make_bad_fd()
 
+        with self.assertRaises(OSError) as ctx:
+            os.get_inheritable(fd)
+        self.assertEqual(ctx.exception.errno, errno.EBADF)
+
         with self.assertRaises(OSError) as ctx:
             os.set_inheritable(fd, True)
         self.assertEqual(ctx.exception.errno, errno.EBADF)