gh-97897: Prevent os.mkfifo and os.mknod segfaults with macOS 13 SDK

Lib/test/test_posix.py

@@ -2090,6 +2090,28 @@ def test_mkdir(self):
             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):

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 opton with either os.mkfifo() or os.mknod() can 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.

Modules/posixmodule.c

@@ -91,6 +91,8 @@
 #  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, *)
 
@@ -175,6 +177,8 @@
 #  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
 
 
@@ -10619,18 +10623,35 @@ 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;
 
@@ -10671,18 +10692,33 @@ 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;
 
@@ -15525,6 +15561,14 @@ 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
@@ -15658,11 +15702,11 @@ 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