bpo-30065: Fixed arguments validation in _posixsubprocess.fork_exec(). (#1110)

Lib/multiprocessing/util.py

@@ -386,7 +386,7 @@ def _close_stdin():
 
 def spawnv_passfds(path, args, passfds):
     import _posixsubprocess
-    passfds = sorted(passfds)
+    passfds = tuple(sorted(map(int, passfds)))
     errpipe_read, errpipe_write = os.pipe()
     try:
         return _posixsubprocess.fork_exec(

Lib/subprocess.py

@@ -1252,7 +1252,8 @@ class Popen(object):
                     fds_to_keep.add(errpipe_write)
                     self.pid = _posixsubprocess.fork_exec(
                             args, executable_list,
-                            close_fds, sorted(fds_to_keep), cwd, env_list,
+                            close_fds, tuple(sorted(map(int, fds_to_keep))),
+                            cwd, env_list,
                             p2cread, p2cwrite, c2pread, c2pwrite,
                             errread, errwrite,
                             errpipe_read, errpipe_write,

Lib/test/test_capi.py

@@ -98,7 +98,7 @@ class CAPITest(unittest.TestCase):
             def __len__(self):
                 return 1
         self.assertRaises(TypeError, _posixsubprocess.fork_exec,
-                          1,Z(),3,[1, 2],5,6,7,8,9,10,11,12,13,14,15,16,17)
+                          1,Z(),3,(1, 2),5,6,7,8,9,10,11,12,13,14,15,16,17)
         # Issue #15736: overflow in _PySequence_BytesToCharpArray()
         class Z(object):
             def __len__(self):
@@ -106,7 +106,7 @@ class CAPITest(unittest.TestCase):
             def __getitem__(self, i):
                 return b'x'
         self.assertRaises(MemoryError, _posixsubprocess.fork_exec,
-                          1,Z(),3,[1, 2],5,6,7,8,9,10,11,12,13,14,15,16,17)
+                          1,Z(),3,(1, 2),5,6,7,8,9,10,11,12,13,14,15,16,17)
 
     @unittest.skipUnless(_posixsubprocess, '_posixsubprocess required for this test.')
     def test_subprocess_fork_exec(self):
@@ -116,7 +116,7 @@ class CAPITest(unittest.TestCase):
 
         # Issue #15738: crash in subprocess_fork_exec()
         self.assertRaises(TypeError, _posixsubprocess.fork_exec,
-                          Z(),[b'1'],3,[1, 2],5,6,7,8,9,10,11,12,13,14,15,16,17)
+                          Z(),[b'1'],3,(1, 2),5,6,7,8,9,10,11,12,13,14,15,16,17)
 
     @unittest.skipIf(MISSING_C_DOCSTRINGS,
                      "Signature information for builtins requires docstrings")

Lib/test/test_subprocess.py

@@ -2418,7 +2418,7 @@ class POSIXProcessTestCase(BaseTestCase):
                 with self.assertRaises(TypeError):
                     _posixsubprocess.fork_exec(
                         args, exe_list,
-                        True, [], cwd, env_list,
+                        True, (), cwd, env_list,
                         -1, -1, -1, -1,
                         1, 2, 3, 4,
                         True, True, func)
@@ -2430,6 +2430,16 @@ class POSIXProcessTestCase(BaseTestCase):
     def test_fork_exec_sorted_fd_sanity_check(self):
         # Issue #23564: sanity check the fork_exec() fds_to_keep sanity check.
         import _posixsubprocess
+        class BadInt:
+            first = True
+            def __init__(self, value):
+                self.value = value
+            def __int__(self):
+                if self.first:
+                    self.first = False
+                    return self.value
+                raise ValueError
+
         gc_enabled = gc.isenabled()
         try:
             gc.enable()
@@ -2440,6 +2450,7 @@ class POSIXProcessTestCase(BaseTestCase):
                 (18, 23, 42, 2**63),  # Out of range.
                 (5, 4),  # Not sorted.
                 (6, 7, 7, 8),  # Duplicate.
+                (BadInt(1), BadInt(2)),
             ):
                 with self.assertRaises(
                         ValueError,

Modules/_posixsubprocess.c

@@ -111,13 +111,17 @@ _is_fdescfs_mounted_on_dev_fd(void)
 static int
 _sanity_check_python_fd_sequence(PyObject *fd_sequence)
 {
-    Py_ssize_t seq_idx, seq_len = PySequence_Length(fd_sequence);
+    Py_ssize_t seq_idx;
     long prev_fd = -1;
-    for (seq_idx = 0; seq_idx < seq_len; ++seq_idx) {
-        PyObject* py_fd = PySequence_Fast_GET_ITEM(fd_sequence, seq_idx);
-        long iter_fd = PyLong_AsLong(py_fd);
+    for (seq_idx = 0; seq_idx < PyTuple_GET_SIZE(fd_sequence); ++seq_idx) {
+        PyObject* py_fd = PyTuple_GET_ITEM(fd_sequence, seq_idx);
+        long iter_fd;
+        if (!PyLong_Check(py_fd)) {
+            return 1;
+        }
+        iter_fd = PyLong_AsLong(py_fd);
         if (iter_fd < 0 || iter_fd <= prev_fd || iter_fd > INT_MAX) {
-            /* Negative, overflow, not a Long, unsorted, too big for a fd. */
+            /* Negative, overflow, unsorted, too big for a fd. */
             return 1;
         }
         prev_fd = iter_fd;
@@ -132,13 +136,12 @@ _is_fd_in_sorted_fd_sequence(int fd, PyObject *fd_sequence)
 {
     /* Binary search. */
     Py_ssize_t search_min = 0;
-    Py_ssize_t search_max = PySequence_Length(fd_sequence) - 1;
+    Py_ssize_t search_max = PyTuple_GET_SIZE(fd_sequence) - 1;
     if (search_max < 0)
         return 0;
     do {
         long middle = (search_min + search_max) / 2;
-        long middle_fd = PyLong_AsLong(
-                PySequence_Fast_GET_ITEM(fd_sequence, middle));
+        long middle_fd = PyLong_AsLong(PyTuple_GET_ITEM(fd_sequence, middle));
         if (fd == middle_fd)
             return 1;
         if (fd > middle_fd)
@@ -154,9 +157,9 @@ make_inheritable(PyObject *py_fds_to_keep, int errpipe_write)
 {
     Py_ssize_t i, len;
 
-    len = PySequence_Length(py_fds_to_keep);
+    len = PyTuple_GET_SIZE(py_fds_to_keep);
     for (i = 0; i < len; ++i) {
-        PyObject* fdobj = PySequence_Fast_GET_ITEM(py_fds_to_keep, i);
+        PyObject* fdobj = PyTuple_GET_ITEM(py_fds_to_keep, i);
         long fd = PyLong_AsLong(fdobj);
         assert(!PyErr_Occurred());
         assert(0 <= fd && fd <= INT_MAX);
@@ -213,14 +216,13 @@ static void
 _close_fds_by_brute_force(long start_fd, PyObject *py_fds_to_keep)
 {
     long end_fd = safe_get_max_fd();
-    Py_ssize_t num_fds_to_keep = PySequence_Length(py_fds_to_keep);
+    Py_ssize_t num_fds_to_keep = PyTuple_GET_SIZE(py_fds_to_keep);
     Py_ssize_t keep_seq_idx;
     int fd_num;
     /* As py_fds_to_keep is sorted we can loop through the list closing
      * fds inbetween any in the keep list falling within our range. */
     for (keep_seq_idx = 0; keep_seq_idx < num_fds_to_keep; ++keep_seq_idx) {
-        PyObject* py_keep_fd = PySequence_Fast_GET_ITEM(py_fds_to_keep,
-                                                        keep_seq_idx);
+        PyObject* py_keep_fd = PyTuple_GET_ITEM(py_fds_to_keep, keep_seq_idx);
         int keep_fd = PyLong_AsLong(py_keep_fd);
         if (keep_fd < start_fd)
             continue;
@@ -306,7 +308,7 @@ _close_open_fds_safe(int start_fd, PyObject* py_fds_to_keep)
 
 
 /* Close all open file descriptors from start_fd and higher.
- * Do not close any in the sorted py_fds_to_keep list.
+ * Do not close any in the sorted py_fds_to_keep tuple.
  *
  * This function violates the strict use of async signal safe functions. :(
  * It calls opendir(), readdir() and closedir().  Of these, the one most
@@ -562,8 +564,9 @@ subprocess_fork_exec(PyObject* self, PyObject *args)
 #endif
 
     if (!PyArg_ParseTuple(
-            args, "OOpOOOiiiiiiiiiiO:fork_exec",
-            &process_args, &executable_list, &close_fds, &py_fds_to_keep,
+            args, "OOpO!OOiiiiiiiiiiO:fork_exec",
+            &process_args, &executable_list,
+            &close_fds, &PyTuple_Type, &py_fds_to_keep,
             &cwd_obj, &env_list,
             &p2cread, &p2cwrite, &c2pread, &c2pwrite,
             &errread, &errwrite, &errpipe_read, &errpipe_write,
@@ -574,10 +577,6 @@ subprocess_fork_exec(PyObject* self, PyObject *args)
         PyErr_SetString(PyExc_ValueError, "errpipe_write must be >= 3");
         return NULL;
     }
-    if (PySequence_Length(py_fds_to_keep) < 0) {
-        PyErr_SetString(PyExc_ValueError, "cannot get length of fds_to_keep");
-        return NULL;
-    }
     if (_sanity_check_python_fd_sequence(py_fds_to_keep)) {
         PyErr_SetString(PyExc_ValueError, "bad value(s) in fds_to_keep");
         return NULL;
@@ -631,6 +630,10 @@ subprocess_fork_exec(PyObject* self, PyObject *args)
             goto cleanup;
         for (arg_num = 0; arg_num < num_args; ++arg_num) {
             PyObject *borrowed_arg, *converted_arg;
+            if (PySequence_Fast_GET_SIZE(fast_args) != num_args) {
+                PyErr_SetString(PyExc_RuntimeError, "args changed during iteration");
+                goto cleanup;
+            }
             borrowed_arg = PySequence_Fast_GET_ITEM(fast_args, arg_num);
             if (PyUnicode_FSConverter(borrowed_arg, &converted_arg) == 0)
                 goto cleanup;