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, 111 insertions, 0 deletions

diff --git a/drivers/mfd/wm831x-spi.c b/drivers/mfd/wm831x-spi.c
new file mode 100644
index 000000000..54c872679
--- /dev/null
+++ b/drivers/mfd/wm831x-spi.c
@@ -0,0 +1,111 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * wm831x-spi.c  --  SPI access for Wolfson WM831x PMICs
+ *
+ * Copyright 2009,2010 Wolfson Microelectronics PLC.
+ *
+ * Author: Mark Brown <broonie@opensource.wolfsonmicro.com>
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/of.h>
+#include <linux/pm.h>
+#include <linux/spi/spi.h>
+#include <linux/regmap.h>
+#include <linux/err.h>
+
+#include <linux/mfd/wm831x/core.h>
+
+static int wm831x_spi_probe(struct spi_device *spi)
+{
+	struct wm831x_pdata *pdata = dev_get_platdata(&spi->dev);
+	struct wm831x *wm831x;
+	enum wm831x_parent type;
+	int ret;
+
+	type = (uintptr_t)spi_get_device_match_data(spi);
+	if (!type) {
+		dev_err(&spi->dev, "Failed to match device\n");
+		return -ENODEV;
+	}
+
+	wm831x = devm_kzalloc(&spi->dev, sizeof(struct wm831x), GFP_KERNEL);
+	if (wm831x == NULL)
+		return -ENOMEM;
+
+	spi->mode = SPI_MODE_0;
+
+	spi_set_drvdata(spi, wm831x);
+	wm831x->dev = &spi->dev;
+	wm831x->type = type;
+
+	wm831x->regmap = devm_regmap_init_spi(spi, &wm831x_regmap_config);
+	if (IS_ERR(wm831x->regmap)) {
+		ret = PTR_ERR(wm831x->regmap);
+		dev_err(wm831x->dev, "Failed to allocate register map: %d\n",
+			ret);
+		return ret;
+	}
+
+	if (pdata)
+		memcpy(&wm831x->pdata, pdata, sizeof(*pdata));
+
+	return wm831x_device_init(wm831x, spi->irq);
+}
+
+static int wm831x_spi_suspend(struct device *dev)
+{
+	struct wm831x *wm831x = dev_get_drvdata(dev);
+
+	return wm831x_device_suspend(wm831x);
+}
+
+static int wm831x_spi_poweroff(struct device *dev)
+{
+	struct wm831x *wm831x = dev_get_drvdata(dev);
+
+	wm831x_device_shutdown(wm831x);
+
+	return 0;
+}
+
+static const struct dev_pm_ops wm831x_spi_pm = {
+	.freeze = wm831x_spi_suspend,
+	.suspend = wm831x_spi_suspend,
+	.poweroff = wm831x_spi_poweroff,
+};
+
+static const struct spi_device_id wm831x_spi_ids[] = {
+	{ "wm8310", WM8310 },
+	{ "wm8311", WM8311 },
+	{ "wm8312", WM8312 },
+	{ "wm8320", WM8320 },
+	{ "wm8321", WM8321 },
+	{ "wm8325", WM8325 },
+	{ "wm8326", WM8326 },
+	{ },
+};
+
+static struct spi_driver wm831x_spi_driver = {
+	.driver = {
+		.name	= "wm831x",
+		.pm	= &wm831x_spi_pm,
+		.of_match_table = of_match_ptr(wm831x_of_match),
+		.suppress_bind_attrs = true,
+	},
+	.id_table	= wm831x_spi_ids,
+	.probe		= wm831x_spi_probe,
+};
+
+static int __init wm831x_spi_init(void)
+{
+	int ret;
+
+	ret = spi_register_driver(&wm831x_spi_driver);
+	if (ret != 0)
+		pr_err("Failed to register WM831x SPI driver: %d\n", ret);
+
+	return 0;
+}
+subsys_initcall(wm831x_spi_init);