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, 68 insertions, 0 deletions

diff --git a/drivers/mfd/cs40l50-i2c.c b/drivers/mfd/cs40l50-i2c.c
new file mode 100644
index 000000000..639be743d
--- /dev/null
+++ b/drivers/mfd/cs40l50-i2c.c
@@ -0,0 +1,68 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * CS40L50 Advanced Haptic Driver with waveform memory,
+ * integrated DSP, and closed-loop algorithms
+ *
+ * Copyright 2024 Cirrus Logic, Inc.
+ *
+ * Author: James Ogletree <james.ogletree@cirrus.com>
+ */
+
+#include <linux/i2c.h>
+#include <linux/mfd/cs40l50.h>
+
+static int cs40l50_i2c_probe(struct i2c_client *i2c)
+{
+	struct cs40l50 *cs40l50;
+
+	cs40l50 = devm_kzalloc(&i2c->dev, sizeof(*cs40l50), GFP_KERNEL);
+	if (!cs40l50)
+		return -ENOMEM;
+
+	i2c_set_clientdata(i2c, cs40l50);
+
+	cs40l50->dev = &i2c->dev;
+	cs40l50->irq = i2c->irq;
+
+	cs40l50->regmap = devm_regmap_init_i2c(i2c, &cs40l50_regmap);
+	if (IS_ERR(cs40l50->regmap))
+		return dev_err_probe(cs40l50->dev, PTR_ERR(cs40l50->regmap),
+				     "Failed to initialize register map\n");
+
+	return cs40l50_probe(cs40l50);
+}
+
+static void cs40l50_i2c_remove(struct i2c_client *i2c)
+{
+	struct cs40l50 *cs40l50 = i2c_get_clientdata(i2c);
+
+	cs40l50_remove(cs40l50);
+}
+
+static const struct i2c_device_id cs40l50_id_i2c[] = {
+	{ "cs40l50" },
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, cs40l50_id_i2c);
+
+static const struct of_device_id cs40l50_of_match[] = {
+	{ .compatible = "cirrus,cs40l50" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, cs40l50_of_match);
+
+static struct i2c_driver cs40l50_i2c_driver = {
+	.driver = {
+		.name = "cs40l50",
+		.of_match_table = cs40l50_of_match,
+		.pm = pm_ptr(&cs40l50_pm_ops),
+	},
+	.id_table = cs40l50_id_i2c,
+	.probe = cs40l50_i2c_probe,
+	.remove = cs40l50_i2c_remove,
+};
+module_i2c_driver(cs40l50_i2c_driver);
+
+MODULE_DESCRIPTION("CS40L50 I2C Driver");
+MODULE_AUTHOR("James Ogletree, Cirrus Logic Inc. <james.ogletree@cirrus.com>");
+MODULE_LICENSE("GPL");