swig: guard against silent attribute typos on SWIG objects

Add __setattr__ to libnvme_global_ctx, libnvme_host,
libnvme_subsystem, and libnvme_ctrl. Without this guard, a caller
writing e.g. ctrl.dhchap_key = x (a typo for dhchap_ctrl_key) would
silently create a new Python instance attribute and discard the value
instead of calling the C-level property setter. This has already caused
a real bug in nvme-stas.

The guard passes through 'this' and '_'-prefixed names (SWIG internals
and GC-anchoring refs set by %pythonappend blocks), walks the MRO to
invoke writable property setters, and raises AttributeError for
everything else — covering both unknown names and %immutable properties.

Also reject unknown keys in the ctrl constructor dict. Previously a
typo in a dict key (e.g. 'subsysnqn_typo') was silently ignored. Now
any unrecognised key raises KeyError at the end of the existing dispatch
loop, with no second pass over the dict.

Add tests/test-setattr.py to cover: valid writable property, typo,
read-only property, unknown attribute, unknown dict key, and missing
required dict key.

Signed-off-by: Martin Belanger <[email protected]>
Assisted-by: Claude Sonnet 4.6 <[email protected]>

Author: Martin Belanger

libnvme/libnvme/meson.build

@@ -84,6 +84,7 @@ if want_python
         [ 'sigsegv-during-gc', [ files('tests/gc.py'), ] ],
         [ 'read-nbft-file', [ files('tests/test-nbft.py'), '--filename', join_paths(meson.current_source_dir(), 'tests', 'NBFT') ] ],
         [ 'object-properties-and-errors', [ files('tests/test-objects.py'), ] ],
+        [ 'setattr-guards', [ files('tests/test-setattr.py'), ] ],
     ]
     foreach test: py_tests
         description = test[0]

libnvme/libnvme/nvme.i

@@ -105,6 +105,14 @@ static inline PyObject *Py_NewRef(PyObject *obj)
 		cfg = libnvmf_context_get_fabrics_config(fctx);
 
 		while (PyDict_Next(dict, &pos, &key, &value)) {
+			/* Already consumed above via dict_get_str() */
+			if (!PyUnicode_CompareWithASCIIString(key, "subsysnqn") ||
+			    !PyUnicode_CompareWithASCIIString(key, "transport") ||
+			    !PyUnicode_CompareWithASCIIString(key, "traddr") ||
+			    !PyUnicode_CompareWithASCIIString(key, "trsvcid") ||
+			    !PyUnicode_CompareWithASCIIString(key, "host_traddr") ||
+			    !PyUnicode_CompareWithASCIIString(key, "host_iface"))
+				continue;
 			if (!PyUnicode_CompareWithASCIIString(key, "queue_size")) {
 				libnvme_fabrics_config_set_queue_size(cfg, PyLong_AsLong(value));
 				continue;
@@ -216,7 +224,8 @@ static inline PyObject *Py_NewRef(PyObject *obj)
 				has_persistent = true;
 				continue;
 			}
-			/* Unknown keys are silently ignored */
+			PyErr_Format(PyExc_KeyError, "unknown ctrl config key: '%U'", key);
+			return -1;
 		}
 
 		if (hostnqn || hostid)
@@ -686,6 +695,20 @@ struct libnvme_ns {
 	    while h:
 	        yield h
 	        h = libnvme_next_host(self, h)
+	def __setattr__(self, name, value):
+	    if name == 'this' or name.startswith('_'):
+	        object.__setattr__(self, name, value)
+	        return
+	    for klass in type(self).__mro__:
+	        attr = klass.__dict__.get(name)
+	        if attr is not None:
+	            if isinstance(attr, property) and attr.fset is not None:
+	                attr.fset(self, value)
+	                return
+	            break
+	    raise AttributeError(
+	        f"'{type(self).__name__}' object has no writable attribute '{name}'"
+	    )
 	%}
 	void refresh_topology() {
 		libnvme_refresh_topology($self);
@@ -750,6 +773,20 @@ struct libnvme_ns {
 	    while s:
 	        yield s
 	        s = libnvme_next_subsystem(self, s)
+	def __setattr__(self, name, value):
+	    if name == 'this' or name.startswith('_'):
+	        object.__setattr__(self, name, value)
+	        return
+	    for klass in type(self).__mro__:
+	        attr = klass.__dict__.get(name)
+	        if attr is not None:
+	            if isinstance(attr, property) and attr.fset is not None:
+	                attr.fset(self, value)
+	                return
+	            break
+	    raise AttributeError(
+	        f"'{type(self).__name__}' object has no writable attribute '{name}'"
+	    )
 	%}
 }
 
@@ -806,6 +843,20 @@ struct libnvme_ns {
 	    while ns:
 	        yield ns
 	        ns = libnvme_subsystem_next_ns(self, ns)
+	def __setattr__(self, name, value):
+	    if name == 'this' or name.startswith('_'):
+	        object.__setattr__(self, name, value)
+	        return
+	    for klass in type(self).__mro__:
+	        attr = klass.__dict__.get(name)
+	        if attr is not None:
+	            if isinstance(attr, property) and attr.fset is not None:
+	                attr.fset(self, value)
+	                return
+	            break
+	    raise AttributeError(
+	        f"'{type(self).__name__}' object has no writable attribute '{name}'"
+	    )
 	%}
 	%immutable name;
 	const char *name;
@@ -1035,6 +1086,20 @@ struct libnvme_ns {
 	    while ns:
 	        yield ns
 	        ns = libnvme_ctrl_next_ns(self, ns)
+	def __setattr__(self, name, value):
+	    if name == 'this' or name.startswith('_'):
+	        object.__setattr__(self, name, value)
+	        return
+	    for klass in type(self).__mro__:
+	        attr = klass.__dict__.get(name)
+	        if attr is not None:
+	            if isinstance(attr, property) and attr.fset is not None:
+	                attr.fset(self, value)
+	                return
+	            break
+	    raise AttributeError(
+	        f"'{type(self).__name__}' object has no writable attribute '{name}'"
+	    )
 	%}
 }
 

libnvme/libnvme/tests/test-setattr.py

@@ -0,0 +1,63 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+# This file is part of libnvme.
+# Copyright (c) 2026, Dell Technologies Inc. or its subsidiaries.
+# Authors: Martin Belanger <[email protected]>
+"""Tests that __setattr__ guards on SWIG-generated classes raise on bad names."""
+
+import unittest
+from libnvme import nvme
+
+
+class TestCtrlSetattr(unittest.TestCase):
+
+    def setUp(self):
+        self.ctx = nvme.global_ctx()
+        self.ctrl = nvme.ctrl(self.ctx, {
+            'subsysnqn': nvme.NVME_DISC_SUBSYS_NAME,
+            'transport': 'loop',
+        })
+
+    def test_valid_writable_property(self):
+        """Writing a valid writable property must not raise."""
+        self.ctrl.discovery_ctrl = True
+
+    def test_typo_raises(self):
+        """A typo in a property name must raise AttributeError immediately."""
+        with self.assertRaises(AttributeError):
+            self.ctrl.dhchap_key = 'somekey'   # correct name is dhchap_ctrl_key
+
+    def test_readonly_raises(self):
+        """Writing a read-only (%immutable) property must raise AttributeError."""
+        with self.assertRaises(AttributeError):
+            self.ctrl.transport = 'tcp'
+
+    def test_unknown_attr_raises(self):
+        """A completely unknown attribute name must raise AttributeError."""
+        with self.assertRaises(AttributeError):
+            self.ctrl.does_not_exist = 42
+
+
+class TestCtrlDictValidation(unittest.TestCase):
+
+    def setUp(self):
+        self.ctx = nvme.global_ctx()
+
+    def test_unknown_dict_key_raises(self):
+        """An unknown key in the constructor dict must raise KeyError."""
+        with self.assertRaises(KeyError):
+            nvme.ctrl(self.ctx, {
+                'subsysnqn': nvme.NVME_DISC_SUBSYS_NAME,
+                'transport': 'loop',
+                'typo_key': 'value',
+            })
+
+    def test_missing_required_key_raises(self):
+        """Omitting a required key (subsysnqn or transport) must raise KeyError."""
+        with self.assertRaises(KeyError):
+            nvme.ctrl(self.ctx, {'transport': 'loop'})
+        with self.assertRaises(KeyError):
+            nvme.ctrl(self.ctx, {'subsysnqn': nvme.NVME_DISC_SUBSYS_NAME})
+
+
+if __name__ == '__main__':
+    unittest.main()