selftests/bpf: Reject graph kptr use after RCU unlockgrafted

Add a sleepable verifier test that loads a graph-node local kptr in an
explicit RCU read-side critical section, then passes its node to
bpf_rbtree_remove() after the section ends.

Before the verifier fix, the stale NON_OWN_REF flag makes the node look like
a live borrowed reference and the program is accepted. After the fix, the
pointer is demoted without NON_OWN_REF and the graph kfunc argument is
rejected.

Also exercise a graph kptr loaded while a spin lock provides implicit RCU
protection. The pointer must be invalidated when the lock is released, which
guards the required ordering between non-owning-reference invalidation and
RCU demotion.

Update the existing fault-protected load test state description. The
post-unlock pointer no longer carries NON_OWN_REF, but remains readable
because the load is rewritten to use BPF_PROBE_MEM.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 77 insertions, 0 deletions

diff --git a/drivers/soc/qcom/rpm-proc.c b/drivers/soc/qcom/rpm-proc.c
new file mode 100644
index 000000000..2466d0400
--- /dev/null
+++ b/drivers/soc/qcom/rpm-proc.c
@@ -0,0 +1,77 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright (c) 2021-2023, Stephan Gerhold <stephan@gerhold.net> */
+
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/rpmsg/qcom_smd.h>
+
+static int rpm_proc_probe(struct platform_device *pdev)
+{
+	struct qcom_smd_edge *edge = NULL;
+	struct device *dev = &pdev->dev;
+	struct device_node *edge_node;
+	int ret;
+
+	edge_node = of_get_child_by_name(dev->of_node, "smd-edge");
+	if (edge_node) {
+		edge = qcom_smd_register_edge(dev, edge_node);
+		of_node_put(edge_node);
+		if (IS_ERR(edge))
+			return dev_err_probe(dev, PTR_ERR(edge),
+					     "Failed to register smd-edge\n");
+	}
+
+	ret = devm_of_platform_populate(dev);
+	if (ret) {
+		dev_err(dev, "Failed to populate child devices: %d\n", ret);
+		goto err;
+	}
+
+	platform_set_drvdata(pdev, edge);
+	return 0;
+err:
+	if (edge)
+		qcom_smd_unregister_edge(edge);
+	return ret;
+}
+
+static void rpm_proc_remove(struct platform_device *pdev)
+{
+	struct qcom_smd_edge *edge = platform_get_drvdata(pdev);
+
+	if (edge)
+		qcom_smd_unregister_edge(edge);
+}
+
+static const struct of_device_id rpm_proc_of_match[] = {
+	{ .compatible = "qcom,rpm-proc", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, rpm_proc_of_match);
+
+static struct platform_driver rpm_proc_driver = {
+	.probe = rpm_proc_probe,
+	.remove = rpm_proc_remove,
+	.driver = {
+		.name = "qcom-rpm-proc",
+		.of_match_table = rpm_proc_of_match,
+	},
+};
+
+static int __init rpm_proc_init(void)
+{
+	return platform_driver_register(&rpm_proc_driver);
+}
+arch_initcall(rpm_proc_init);
+
+static void __exit rpm_proc_exit(void)
+{
+	platform_driver_unregister(&rpm_proc_driver);
+}
+module_exit(rpm_proc_exit);
+
+MODULE_DESCRIPTION("Qualcomm RPM processor/subsystem driver");
+MODULE_AUTHOR("Stephan Gerhold <stephan@gerhold.net>");
+MODULE_LICENSE("GPL");