Validate effect bytes before native force-feedback upload

src/evdev/input.c

@@ -482,7 +482,13 @@ upload_effect(PyObject *self, PyObject *args)
     ret = PyArg_ParseTuple(args, "iO", &fd, &effect_data);
     if (!ret) return NULL;
 
-    void* data = PyBytes_AsString(effect_data);
+    char* data;
+    Py_ssize_t data_size;
+    if (PyBytes_AsStringAndSize(effect_data, &data, &data_size) < 0) return NULL;
+    if (data_size < (Py_ssize_t)sizeof(struct ff_effect)) {
+        PyErr_SetString(PyExc_ValueError, "effect data is too short for struct ff_effect");
+        return NULL;
+    }
     struct ff_effect effect = {};
     memmove(&effect, data, sizeof(struct ff_effect));
 

tests/test_input.py

@@ -0,0 +1,62 @@
+"""Validate the native input API without requiring an input device."""
+
+import ctypes
+import errno
+import subprocess
+import sys
+
+import pytest
+
+from evdev import _input, device, ff
+
+
+@pytest.mark.parametrize("expression", ["None", "0", "'effect'", "[]", "bytearray(64)", "memoryview(bytes(64))"])
+def test_upload_effect_rejects_non_bytes(expression):
+    # A conversion failure used to dereference NULL. Keep a broken extension
+    # from crashing the test runner, and do not leave core dumps behind.
+    code = """
+import resource
+import sys
+from evdev import _input
+resource.setrlimit(resource.RLIMIT_CORE, (0, 0))
+try:
+    _input.upload_effect(-1, eval(sys.argv[1]))
+except TypeError:
+    pass
+else:
+    raise AssertionError('expected TypeError')
+"""
+    result = subprocess.run([sys.executable, "-c", code, expression], check=False, capture_output=True, text=True)
+    assert result.returncode == 0, result.stderr
+
+
+@pytest.mark.parametrize("size", [0, 1, ctypes.sizeof(ff.Effect) - 1])
+def test_upload_effect_rejects_short_bytes(size):
+    with pytest.raises(ValueError, match="effect data"):
+        _input.upload_effect(-1, bytes(size))
+
+
+class EffectBytes(bytes):
+    pass
+
+
+@pytest.mark.parametrize("data", [bytes(ff.Effect()), bytes(ff.Effect()) + b"extra", EffectBytes(bytes(ff.Effect()))])
+def test_upload_effect_preserves_ioctl_errors(data):
+    # A complete effect must reach ioctl, including bytes subclasses and the
+    # previously accepted trailing bytes. Invalid descriptors remain EBADF.
+    with pytest.raises(OSError) as error:
+        _input.upload_effect(-1, data)
+    assert error.value.errno == errno.EBADF
+
+
+def test_device_upload_effect_uses_complete_structure():
+    input_device = device.InputDevice.__new__(device.InputDevice)
+    input_device.fd = -1
+    effect = ff.Effect()
+    effect.id = -1
+    with pytest.raises(OSError) as error:
+        input_device.upload_effect(effect)
+    assert error.value.errno == errno.EBADF
+    assert effect.id == -1
+    # No descriptor is owned by this stand-in InputDevice.
+    input_device.fd = None