gh-126220: Fix crash on calls to `_lsprof.Profiler` methods with 0 args (backportable) (#126271)

Co-authored-by: Erlend E. Aasland <erlend.aasland@protonmail.com>

Lib/test/test_cprofile.py

@@ -30,6 +30,22 @@ class CProfileTest(ProfileTest):
 
             self.assertEqual(cm.unraisable.exc_type, TypeError)
 
+    def test_crash_with_not_enough_args(self):
+        # gh-126220
+        import _lsprof
+
+        for profile in [_lsprof.Profiler(), cProfile.Profile()]:
+            for method in [
+                "_pystart_callback",
+                "_pyreturn_callback",
+                "_ccall_callback",
+                "_creturn_callback",
+            ]:
+                with self.subTest(profile=profile, method=method):
+                    method_obj = getattr(profile, method)
+                    with self.assertRaises(TypeError):
+                        method_obj()  # should not crash
+
     def test_evil_external_timer(self):
         # gh-120289
         # Disabling profiler in external timer should not crash

Misc/NEWS.d/next/Library/2024-10-31-14-06-28.gh-issue-126220.uJAJCU.rst

@@ -0,0 +1,2 @@
+Fix crash in :class:`!cProfile.Profile` and :class:`!_lsprof.Profiler` when their
+callbacks were directly called with 0 arguments.

Modules/_lsprof.c

@@ -608,6 +608,12 @@ setBuiltins(ProfilerObject *pObj, int nvalue)
 
 PyObject* pystart_callback(ProfilerObject* self, PyObject *const *args, Py_ssize_t size)
 {
+    if (size < 2) {
+        PyErr_Format(PyExc_TypeError,
+                     "_pystart_callback expected 2 arguments, got %zd",
+                     size);
+        return NULL;
+    }
     PyObject* code = args[0];
     ptrace_enter_call((PyObject*)self, (void *)code, (PyObject *)code);
 
@@ -616,6 +622,12 @@ PyObject* pystart_callback(ProfilerObject* self, PyObject *const *args, Py_ssize
 
 PyObject* pyreturn_callback(ProfilerObject* self, PyObject *const *args, Py_ssize_t size)
 {
+    if (size < 3) {
+        PyErr_Format(PyExc_TypeError,
+                     "_pyreturn_callback expected 3 arguments, got %zd",
+                     size);
+        return NULL;
+    }
     PyObject* code = args[0];
     ptrace_leave_call((PyObject*)self, (void *)code);
 
@@ -651,6 +663,12 @@ PyObject* get_cfunc_from_callable(PyObject* callable, PyObject* self_arg, PyObje
 
 PyObject* ccall_callback(ProfilerObject* self, PyObject *const *args, Py_ssize_t size)
 {
+    if (size < 4) {
+        PyErr_Format(PyExc_TypeError,
+                     "_ccall_callback expected 4 arguments, got %zd",
+                     size);
+        return NULL;
+    }
     if (self->flags & POF_BUILTINS) {
         PyObject* callable = args[2];
         PyObject* self_arg = args[3];
@@ -669,6 +687,12 @@ PyObject* ccall_callback(ProfilerObject* self, PyObject *const *args, Py_ssize_t
 
 PyObject* creturn_callback(ProfilerObject* self, PyObject *const *args, Py_ssize_t size)
 {
+    if (size < 4) {
+        PyErr_Format(PyExc_TypeError,
+                     "_creturn_callback expected 4 arguments, got %zd",
+                     size);
+        return NULL;
+    }
     if (self->flags & POF_BUILTINS) {
         PyObject* callable = args[2];
         PyObject* self_arg = args[3];