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, 72 insertions, 0 deletions

diff --git a/drivers/input/touchscreen/ad7879-spi.c b/drivers/input/touchscreen/ad7879-spi.c
new file mode 100644
index 000000000..064968fe5
--- /dev/null
+++ b/drivers/input/touchscreen/ad7879-spi.c
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * AD7879/AD7889 touchscreen (SPI bus)
+ *
+ * Copyright (C) 2008-2010 Michael Hennerich, Analog Devices Inc.
+ */
+
+#include <linux/input.h>	/* BUS_SPI */
+#include <linux/pm.h>
+#include <linux/spi/spi.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/regmap.h>
+
+#include "ad7879.h"
+
+#define AD7879_DEVID		0x7A	/* AD7879/AD7889 */
+
+#define MAX_SPI_FREQ_HZ      5000000
+
+#define AD7879_CMD_MAGIC     0xE0
+#define AD7879_CMD_READ      BIT(2)
+
+static const struct regmap_config ad7879_spi_regmap_config = {
+	.reg_bits = 16,
+	.val_bits = 16,
+	.max_register = 15,
+	.read_flag_mask = AD7879_CMD_MAGIC | AD7879_CMD_READ,
+	.write_flag_mask = AD7879_CMD_MAGIC,
+};
+
+static int ad7879_spi_probe(struct spi_device *spi)
+{
+	struct regmap *regmap;
+
+	/* don't exceed max specified SPI CLK frequency */
+	if (spi->max_speed_hz > MAX_SPI_FREQ_HZ) {
+		dev_err(&spi->dev, "SPI CLK %d Hz?\n", spi->max_speed_hz);
+		return -EINVAL;
+	}
+
+	regmap = devm_regmap_init_spi(spi, &ad7879_spi_regmap_config);
+	if (IS_ERR(regmap))
+		return PTR_ERR(regmap);
+
+	return ad7879_probe(&spi->dev, regmap, spi->irq, BUS_SPI, AD7879_DEVID);
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id ad7879_spi_dt_ids[] = {
+	{ .compatible = "adi,ad7879", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, ad7879_spi_dt_ids);
+#endif
+
+static struct spi_driver ad7879_spi_driver = {
+	.driver = {
+		.name		= "ad7879",
+		.dev_groups	= ad7879_groups,
+		.pm		= &ad7879_pm_ops,
+		.of_match_table	= of_match_ptr(ad7879_spi_dt_ids),
+	},
+	.probe		= ad7879_spi_probe,
+};
+
+module_spi_driver(ad7879_spi_driver);
+
+MODULE_AUTHOR("Michael Hennerich <michael.hennerich@analog.com>");
+MODULE_DESCRIPTION("AD7879(-1) touchscreen SPI bus driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("spi:ad7879");