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, 93 insertions, 0 deletions

diff --git a/drivers/mfd/cs42l43-i2c.c b/drivers/mfd/cs42l43-i2c.c
new file mode 100644
index 000000000..44ad63129
--- /dev/null
+++ b/drivers/mfd/cs42l43-i2c.c
@@ -0,0 +1,93 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * CS42L43 I2C driver
+ *
+ * Copyright (C) 2022-2023 Cirrus Logic, Inc. and
+ *                         Cirrus Logic International Semiconductor Ltd.
+ */
+
+#include <linux/array_size.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/mfd/cs42l43.h>
+#include <linux/mfd/cs42l43-regs.h>
+#include <linux/module.h>
+#include <linux/pm.h>
+#include <linux/regmap.h>
+
+#include "cs42l43.h"
+
+static const struct regmap_config cs42l43_i2c_regmap = {
+	.reg_bits		= 32,
+	.reg_stride		= 4,
+	.val_bits		= 32,
+	.reg_format_endian	= REGMAP_ENDIAN_BIG,
+	.val_format_endian	= REGMAP_ENDIAN_BIG,
+
+	.max_register		= CS42L43_MCU_RAM_MAX,
+	.readable_reg		= cs42l43_readable_register,
+	.volatile_reg		= cs42l43_volatile_register,
+	.precious_reg		= cs42l43_precious_register,
+
+	.cache_type		= REGCACHE_MAPLE,
+	.reg_defaults		= cs42l43_reg_default,
+	.num_reg_defaults	= ARRAY_SIZE(cs42l43_reg_default),
+};
+
+static int cs42l43_i2c_probe(struct i2c_client *i2c)
+{
+	struct cs42l43 *cs42l43;
+
+	cs42l43 = devm_kzalloc(&i2c->dev, sizeof(*cs42l43), GFP_KERNEL);
+	if (!cs42l43)
+		return -ENOMEM;
+
+	cs42l43->dev = &i2c->dev;
+	cs42l43->irq = i2c->irq;
+	/* A device on an I2C is always attached by definition. */
+	cs42l43->attached = true;
+	cs42l43->variant_id = (long)device_get_match_data(cs42l43->dev);
+
+	cs42l43->regmap = devm_regmap_init_i2c(i2c, &cs42l43_i2c_regmap);
+	if (IS_ERR(cs42l43->regmap))
+		return dev_err_probe(cs42l43->dev, PTR_ERR(cs42l43->regmap),
+				     "Failed to allocate regmap\n");
+
+	return cs42l43_dev_probe(cs42l43);
+}
+
+#if IS_ENABLED(CONFIG_OF)
+static const struct of_device_id cs42l43_of_match[] = {
+	{ .compatible = "cirrus,cs42l43", .data = (void *)CS42L43_DEVID_VAL },
+	{ .compatible = "cirrus,cs42l43b", .data = (void *)CS42L43B_DEVID_VAL },
+	{}
+};
+MODULE_DEVICE_TABLE(of, cs42l43_of_match);
+#endif
+
+#if IS_ENABLED(CONFIG_ACPI)
+static const struct acpi_device_id cs42l43_acpi_match[] = {
+	{ "CSC4243", CS42L43_DEVID_VAL },
+	{ "CSC2A3B", CS42L43B_DEVID_VAL },
+	{}
+};
+MODULE_DEVICE_TABLE(acpi, cs42l43_acpi_match);
+#endif
+
+static struct i2c_driver cs42l43_i2c_driver = {
+	.driver = {
+		.name			= "cs42l43",
+		.pm			= pm_ptr(&cs42l43_pm_ops),
+		.of_match_table		= of_match_ptr(cs42l43_of_match),
+		.acpi_match_table	= ACPI_PTR(cs42l43_acpi_match),
+	},
+
+	.probe		= cs42l43_i2c_probe,
+};
+module_i2c_driver(cs42l43_i2c_driver);
+
+MODULE_IMPORT_NS("MFD_CS42L43");
+
+MODULE_DESCRIPTION("CS42L43 I2C Driver");
+MODULE_AUTHOR("Charles Keepax <ckeepax@opensource.cirrus.com>");
+MODULE_LICENSE("GPL");