[3.9] gh-97897: Prevent os.mkfifo and os.mknod segfaults with macOS 13 SDK (GH-97944...

The macOS 13 SDK includes support for the `mkfifoat` and `mknodat` system calls.
 Using the `dir_fd` option with either `os.mkfifo` or `os.mknod` could result in a
 segfault if cpython is built with the macOS 13 SDK but run on an earlier
 version of macOS. Prevent this by adding runtime support for detection of
 these system calls ("weaklinking") as is done for other newer syscalls on
 macOS.
(cherry picked from commit 6d0a0191a4e5477bd843e62c24d7f3bcad4fd5fc)

Co-authored-by: Ned Deily <nad@python.org>

diff --git a/Lib/test/test_posix.py b/Lib/test/test_posix.py
index 6ba14547bdd6c45ee822b512afb90787b2cabc97..3c0ddeb0037c67a53766f3c28569bd38940810de 100644 (file)
--- a/Lib/test/test_posix.py
+++ b/Lib/test/test_posix.py
@@ -2040,6 +2040,28 @@ class TestPosixWeaklinking(unittest.TestCase):
             with self.assertRaisesRegex(NotImplementedError, "dir_fd unavailable"):
                 os.mkdir("dir", dir_fd=0)
 
+    def test_mkfifo(self):
+        self._verify_available("HAVE_MKFIFOAT")
+        if self.mac_ver >= (13, 0):
+            self.assertIn("HAVE_MKFIFOAT", posix._have_functions)
+
+        else:
+            self.assertNotIn("HAVE_MKFIFOAT", posix._have_functions)
+
+            with self.assertRaisesRegex(NotImplementedError, "dir_fd unavailable"):
+                os.mkfifo("path", dir_fd=0)
+
+    def test_mknod(self):
+        self._verify_available("HAVE_MKNODAT")
+        if self.mac_ver >= (13, 0):
+            self.assertIn("HAVE_MKNODAT", posix._have_functions)
+
+        else:
+            self.assertNotIn("HAVE_MKNODAT", posix._have_functions)
+
+            with self.assertRaisesRegex(NotImplementedError, "dir_fd unavailable"):
+                os.mknod("path", dir_fd=0)
+
     def test_rename_replace(self):
         self._verify_available("HAVE_RENAMEAT")
         if self.mac_ver >= (10, 10):

diff --git a/Misc/NEWS.d/next/macOS/2022-10-05-15-26-58.gh-issue-97897.Rf-C6u.rst b/Misc/NEWS.d/next/macOS/2022-10-05-15-26-58.gh-issue-97897.Rf-C6u.rst
new file mode 100644 (file)
index 0000000..0d21e98
--- /dev/null
+++ b/Misc/NEWS.d/next/macOS/2022-10-05-15-26-58.gh-issue-97897.Rf-C6u.rst
@@ -0,0 +1,6 @@
+The macOS 13 SDK includes support for the ``mkfifoat`` and ``mknodat`` system calls.
+Using the ``dir_fd`` option with either :func:`os.mkfifo` or :func:`os.mknod` could result in a
+segfault if cpython is built with the macOS 13 SDK but run on an earlier
+version of macOS. Prevent this by adding runtime support for detection of
+these system calls ("weaklinking") as is done for other newer syscalls on
+macOS.

diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 1270af735e2b2c5862b9f3f0c29dfea075312e3d..bf4e648421d3e091d82dbb766488a16fc3303994 100644 (file)
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -79,6 +79,8 @@
 #  define HAVE_FUTIMENS_RUNTIME __builtin_available(macOS 10.13, iOS 11.0, tvOS 11.0, watchOS 4.0, *)
 #  define HAVE_UTIMENSAT_RUNTIME __builtin_available(macOS 10.13, iOS 11.0, tvOS 11.0, watchOS 4.0, *)
 #  define HAVE_PWRITEV_RUNTIME __builtin_available(macOS 11.0, iOS 14.0, tvOS 14.0, watchOS 7.0, *)
+#  define HAVE_MKFIFOAT_RUNTIME __builtin_available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *)
+#  define HAVE_MKNODAT_RUNTIME __builtin_available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *)
 
 #  define HAVE_POSIX_SPAWN_SETSID_RUNTIME __builtin_available(macOS 10.15, *)
 
@@ -163,6 +165,8 @@
 #  define HAVE_FUTIMENS_RUNTIME 1
 #  define HAVE_UTIMENSAT_RUNTIME 1
 #  define HAVE_PWRITEV_RUNTIME 1
+#  define HAVE_MKFIFOAT_RUNTIME 1
+#  define HAVE_MKNODAT_RUNTIME 1
 #endif
 
 
@@ -10482,18 +10486,35 @@ os_mkfifo_impl(PyObject *module, path_t *path, int mode, int dir_fd)
 {
     int result;
     int async_err = 0;
+#ifdef HAVE_MKFIFOAT
+    int mkfifoat_unavailable = 0;
+#endif
 
     do {
         Py_BEGIN_ALLOW_THREADS
 #ifdef HAVE_MKFIFOAT
-        if (dir_fd != DEFAULT_DIR_FD)
-            result = mkfifoat(dir_fd, path->narrow, mode);
-        else
+        if (dir_fd != DEFAULT_DIR_FD) {
+            if (HAVE_MKFIFOAT_RUNTIME) {
+                result = mkfifoat(dir_fd, path->narrow, mode);
+
+            } else {
+                mkfifoat_unavailable = 1;
+                result = 0;
+            }
+        } else
 #endif
             result = mkfifo(path->narrow, mode);
         Py_END_ALLOW_THREADS
     } while (result != 0 && errno == EINTR &&
              !(async_err = PyErr_CheckSignals()));
+
+#ifdef HAVE_MKFIFOAT
+    if (mkfifoat_unavailable) {
+        argument_unavailable_error(NULL, "dir_fd");
+        return NULL;
+    }
+#endif
+
     if (result != 0)
         return (!async_err) ? posix_error() : NULL;
 
@@ -10534,18 +10555,33 @@ os_mknod_impl(PyObject *module, path_t *path, int mode, dev_t device,
 {
     int result;
     int async_err = 0;
+#ifdef HAVE_MKNODAT
+    int mknodat_unavailable = 0;
+#endif
 
     do {
         Py_BEGIN_ALLOW_THREADS
 #ifdef HAVE_MKNODAT
-        if (dir_fd != DEFAULT_DIR_FD)
-            result = mknodat(dir_fd, path->narrow, mode, device);
-        else
+        if (dir_fd != DEFAULT_DIR_FD) {
+            if (HAVE_MKNODAT_RUNTIME) {
+                result = mknodat(dir_fd, path->narrow, mode, device);
+
+            } else {
+                mknodat_unavailable = 1;
+                result = 0;
+            }
+        } else
 #endif
             result = mknod(path->narrow, mode, device);
         Py_END_ALLOW_THREADS
     } while (result != 0 && errno == EINTR &&
              !(async_err = PyErr_CheckSignals()));
+#ifdef HAVE_MKNODAT
+    if (mknodat_unavailable) {
+        argument_unavailable_error(NULL, "dir_fd");
+        return NULL;
+    }
+#endif
     if (result != 0)
         return (!async_err) ? posix_error() : NULL;
 
@@ -15265,6 +15301,14 @@ PROBE(probe_fdopendir, HAVE_FDOPENDIR_RUNTIME)
 PROBE(probe_mkdirat, HAVE_MKDIRAT_RUNTIME)
 #endif
 
+#ifdef HAVE_MKFIFOAT
+PROBE(probe_mkfifoat, HAVE_MKFIFOAT_RUNTIME)
+#endif
+
+#ifdef HAVE_MKNODAT
+PROBE(probe_mknodat, HAVE_MKNODAT_RUNTIME)
+#endif
+
 #ifdef HAVE_RENAMEAT
 PROBE(probe_renameat, HAVE_RENAMEAT_RUNTIME)
 #endif
@@ -15394,11 +15438,11 @@ static const struct have_function {
 #endif
 
 #ifdef HAVE_MKFIFOAT
-    { "HAVE_MKFIFOAT", NULL },
+    { "HAVE_MKFIFOAT", probe_mkfifoat },
 #endif
 
 #ifdef HAVE_MKNODAT
-    { "HAVE_MKNODAT", NULL },
+    { "HAVE_MKNODAT", probe_mknodat },
 #endif
 
 #ifdef HAVE_OPENAT