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, 99 insertions, 0 deletions

diff --git a/drivers/gpio/gpio-tn48m.c b/drivers/gpio/gpio-tn48m.c
new file mode 100644
index 000000000..4fcd0bc24
--- /dev/null
+++ b/drivers/gpio/gpio-tn48m.c
@@ -0,0 +1,99 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Delta TN48M CPLD GPIO driver
+ *
+ * Copyright (C) 2021 Sartura Ltd.
+ *
+ * Author: Robert Marko <robert.marko@sartura.hr>
+ */
+
+#include <linux/device.h>
+#include <linux/gpio/driver.h>
+#include <linux/gpio/regmap.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+enum tn48m_gpio_type {
+	TN48M_GP0 = 1,
+	TN48M_GPI,
+};
+
+struct tn48m_gpio_config {
+	int ngpio;
+	int ngpio_per_reg;
+	enum tn48m_gpio_type type;
+};
+
+static const struct tn48m_gpio_config tn48m_gpo_config = {
+	.ngpio = 4,
+	.ngpio_per_reg = 4,
+	.type = TN48M_GP0,
+};
+
+static const struct tn48m_gpio_config tn48m_gpi_config = {
+	.ngpio = 4,
+	.ngpio_per_reg = 4,
+	.type = TN48M_GPI,
+};
+
+static int tn48m_gpio_probe(struct platform_device *pdev)
+{
+	const struct tn48m_gpio_config *gpio_config;
+	struct gpio_regmap_config config = {};
+	struct regmap *regmap;
+	u32 base;
+	int ret;
+
+	if (!pdev->dev.parent)
+		return -ENODEV;
+
+	gpio_config = device_get_match_data(&pdev->dev);
+	if (!gpio_config)
+		return -ENODEV;
+
+	ret = device_property_read_u32(&pdev->dev, "reg", &base);
+	if (ret)
+		return ret;
+
+	regmap = dev_get_regmap(pdev->dev.parent, NULL);
+	if (!regmap)
+		return -ENODEV;
+
+	config.regmap = regmap;
+	config.parent = &pdev->dev;
+	config.ngpio = gpio_config->ngpio;
+	config.ngpio_per_reg = gpio_config->ngpio_per_reg;
+	switch (gpio_config->type) {
+	case TN48M_GP0:
+		config.reg_set_base = base;
+		break;
+	case TN48M_GPI:
+		config.reg_dat_base = base;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return PTR_ERR_OR_ZERO(devm_gpio_regmap_register(&pdev->dev, &config));
+}
+
+static const struct of_device_id tn48m_gpio_of_match[] = {
+	{ .compatible = "delta,tn48m-gpo", .data = &tn48m_gpo_config },
+	{ .compatible = "delta,tn48m-gpi", .data = &tn48m_gpi_config },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, tn48m_gpio_of_match);
+
+static struct platform_driver tn48m_gpio_driver = {
+	.driver = {
+		.name = "delta-tn48m-gpio",
+		.of_match_table = tn48m_gpio_of_match,
+	},
+	.probe = tn48m_gpio_probe,
+};
+module_platform_driver(tn48m_gpio_driver);
+
+MODULE_AUTHOR("Robert Marko <robert.marko@sartura.hr>");
+MODULE_DESCRIPTION("Delta TN48M CPLD GPIO driver");
+MODULE_LICENSE("GPL");