test: py: add regression test for fit_import_data() stale state

Build an external-data FIT, remove the data-offset property from the
second image so that only its data-size remains, and re-process the
result with mkimage -F. mkimage must reject the malformed FIT with a
clear diagnostic from the hashing stage. Previously the stale per-image
state in fit_import_data() made the import copy the first image's data
into the second image and abort without printing anything.

Signed-off-by: Aristo Chen <aristo.chen@canonical.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

test/py/tests/test_fit_import_data.py

@@ -0,0 +1,89 @@
+# SPDX-License-Identifier: GPL-2.0+
+# Copyright 2026 Canonical Ltd.
+#
+# Test mkimage import of external data in fit_import_data()
+
+"""Regression test for stale per-image state in fit_import_data().
+
+The import loop used to keep the data pointer and external property name
+of the previous image, so an image node carrying data-size but neither
+data-offset nor data-position imported the previous image's data and
+then made mkimage abort without printing any diagnostic. Such a node
+must be skipped by the import and reported by the later processing
+stages instead.
+"""
+
+import os
+import subprocess
+
+import pytest
+
+import fit_util
+
+BASE_ITS = '''
+/dts-v1/;
+
+/ {
+    description = "import-data test";
+
+    images {
+        kernel-1 {
+            description = "first kernel";
+            data = /incbin/("%(kernel1)s");
+            type = "kernel";
+            arch = "sandbox";
+            os = "linux";
+            compression = "none";
+            load = <0x40000>;
+            entry = <0x40000>;
+        };
+        kernel-2 {
+            description = "second kernel";
+            data = /incbin/("%(kernel2)s");
+            type = "kernel";
+            arch = "sandbox";
+            os = "linux";
+            compression = "none";
+            load = <0x80000>;
+            entry = <0x80000>;
+        };
+    };
+
+    configurations {
+        default = "conf-1";
+        conf-1 {
+            kernel = "kernel-1";
+        };
+    };
+};
+'''
+
+
+@pytest.mark.boardspec('sandbox')
+@pytest.mark.requiredtool('dtc')
+@pytest.mark.requiredtool('fdtput')
+def test_fit_import_data_missing_offset(ubman):
+    """An image with data-size but no data-offset must not inherit data"""
+    mkimage = os.path.join(ubman.config.build_dir, 'tools/mkimage')
+    params = {
+        'kernel1': fit_util.make_kernel(ubman, 'imp-kernel1.bin', 'first'),
+        'kernel2': fit_util.make_kernel(ubman, 'imp-kernel2.bin', 'second'),
+    }
+    its = fit_util.make_its(ubman, BASE_ITS, params, 'imp.its')
+    itb = fit_util.make_fname(ubman, 'imp.itb')
+
+    result = subprocess.run([mkimage, '-E', '-f', its, itb],
+                            capture_output=True, text=True)
+    assert result.returncode == 0, result.stderr
+
+    # Remove the offset so that only data-size is left on kernel-2
+    subprocess.run(['fdtput', '-d', itb, '/images/kernel-2', 'data-offset'],
+                   check=True)
+
+    # Re-processing must skip the malformed image in the import, so that
+    # the hashing stage reports it; previously the stale pointer made the
+    # import write kernel-1's data into kernel-2 and abort silently
+    result = subprocess.run([mkimage, '-F', itb],
+                            capture_output=True, text=True)
+    assert result.returncode != 0
+    assert "Can't get image data/size" in result.stderr