of: unittest: fix use-after-free in of_unittest_changeset()

of: unittest: fix use-after-free in of_unittest_changeset()

The variable 'parent' is assigned the value of 'nchangeset' earlier in the
function, meaning both point to the same struct device_node. The call to
of_node_put(nchangeset) can decrement the reference count to zero and
free the node if there are no other holders. After that, the code still
uses 'parent' to check for the presence of a property and to read a
string property, leading to a use-after-free.

Fix this by moving the of_node_put() call after the last access to
'parent', avoiding the UAF.

Fixes: 1c668ea65506 ("of: unittest: Use of_property_present()")
Cc: stable@vger.kernel.org
Signed-off-by: Wentao Liang <vulab@iscas.ac.cn>
Link: https://patch.msgid.link/20260409022233.418103-1-vulab@iscas.ac.cn
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>