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, 74 insertions, 0 deletions

diff --git a/drivers/gpio/gpio-ds4520.c b/drivers/gpio/gpio-ds4520.c
new file mode 100644
index 000000000..5add662a7
--- /dev/null
+++ b/drivers/gpio/gpio-ds4520.c
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2023 Analog Devices, Inc.
+ * Driver for the DS4520 I/O Expander
+ */
+
+#include <linux/device.h>
+#include <linux/gpio/driver.h>
+#include <linux/gpio/regmap.h>
+#include <linux/i2c.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+
+#define DS4520_PULLUP0		0xF0
+#define DS4520_IO_CONTROL0	0xF2
+#define DS4520_IO_STATUS0	0xF8
+
+static const struct regmap_config ds4520_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+};
+
+static int ds4520_gpio_probe(struct i2c_client *client)
+{
+	struct gpio_regmap_config config = { };
+	struct device *dev = &client->dev;
+	struct regmap *regmap;
+	u32 base;
+	int ret;
+
+	ret = device_property_read_u32(dev, "reg", &base);
+	if (ret)
+		return dev_err_probe(dev, ret, "Missing 'reg' property.\n");
+
+	regmap = devm_regmap_init_i2c(client, &ds4520_regmap_config);
+	if (IS_ERR(regmap))
+		return dev_err_probe(dev, PTR_ERR(regmap),
+				     "Failed to allocate register map\n");
+
+	config.regmap = regmap;
+	config.parent = dev;
+
+	config.reg_dat_base = base + DS4520_IO_STATUS0;
+	config.reg_set_base = base + DS4520_PULLUP0;
+	config.reg_dir_out_base = base + DS4520_IO_CONTROL0;
+
+	return PTR_ERR_OR_ZERO(devm_gpio_regmap_register(dev, &config));
+}
+
+static const struct of_device_id ds4520_gpio_of_match_table[] = {
+	{ .compatible = "adi,ds4520-gpio" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, ds4520_gpio_of_match_table);
+
+static const struct i2c_device_id ds4520_gpio_id_table[] = {
+	{ .name = "ds4520-gpio" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, ds4520_gpio_id_table);
+
+static struct i2c_driver ds4520_gpio_driver = {
+	.driver = {
+		.name = "ds4520-gpio",
+		.of_match_table = ds4520_gpio_of_match_table,
+	},
+	.probe = ds4520_gpio_probe,
+	.id_table = ds4520_gpio_id_table,
+};
+module_i2c_driver(ds4520_gpio_driver);
+
+MODULE_DESCRIPTION("DS4520 I/O Expander");
+MODULE_AUTHOR("Okan Sahin <okan.sahin@analog.com>");
+MODULE_LICENSE("GPL");