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, 134 insertions, 0 deletions

diff --git a/drivers/i2c/busses/i2c-versatile.c b/drivers/i2c/busses/i2c-versatile.c
new file mode 100644
index 000000000..a1ab6ef6f
--- /dev/null
+++ b/drivers/i2c/busses/i2c-versatile.c
@@ -0,0 +1,134 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  i2c-versatile.c
+ *
+ *  Copyright (C) 2006 ARM Ltd.
+ *  written by Russell King, Deep Blue Solutions Ltd.
+ */
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/i2c-algo-bit.h>
+#include <linux/init.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/io.h>
+
+#define I2C_CONTROL	0x00
+#define I2C_CONTROLS	0x00
+#define I2C_CONTROLC	0x04
+#define SCL		(1 << 0)
+#define SDA		(1 << 1)
+
+struct i2c_versatile {
+	struct i2c_adapter	 adap;
+	struct i2c_algo_bit_data algo;
+	void __iomem		 *base;
+};
+
+static void i2c_versatile_setsda(void *data, int state)
+{
+	struct i2c_versatile *i2c = data;
+
+	writel(SDA, i2c->base + (state ? I2C_CONTROLS : I2C_CONTROLC));
+}
+
+static void i2c_versatile_setscl(void *data, int state)
+{
+	struct i2c_versatile *i2c = data;
+
+	writel(SCL, i2c->base + (state ? I2C_CONTROLS : I2C_CONTROLC));
+}
+
+static int i2c_versatile_getsda(void *data)
+{
+	struct i2c_versatile *i2c = data;
+	return !!(readl(i2c->base + I2C_CONTROL) & SDA);
+}
+
+static int i2c_versatile_getscl(void *data)
+{
+	struct i2c_versatile *i2c = data;
+	return !!(readl(i2c->base + I2C_CONTROL) & SCL);
+}
+
+static const struct i2c_algo_bit_data i2c_versatile_algo = {
+	.setsda	= i2c_versatile_setsda,
+	.setscl = i2c_versatile_setscl,
+	.getsda	= i2c_versatile_getsda,
+	.getscl = i2c_versatile_getscl,
+	.udelay	= 30,
+	.timeout = HZ,
+};
+
+static int i2c_versatile_probe(struct platform_device *dev)
+{
+	struct i2c_versatile *i2c;
+	int ret;
+
+	i2c = devm_kzalloc(&dev->dev, sizeof(struct i2c_versatile), GFP_KERNEL);
+	if (!i2c)
+		return -ENOMEM;
+
+	i2c->base = devm_platform_get_and_ioremap_resource(dev, 0, NULL);
+	if (IS_ERR(i2c->base))
+		return PTR_ERR(i2c->base);
+
+	writel(SCL | SDA, i2c->base + I2C_CONTROLS);
+
+	i2c->adap.owner = THIS_MODULE;
+	strscpy(i2c->adap.name, "Versatile I2C adapter", sizeof(i2c->adap.name));
+	i2c->adap.algo_data = &i2c->algo;
+	i2c->adap.dev.parent = &dev->dev;
+	i2c->adap.dev.of_node = dev->dev.of_node;
+	i2c->algo = i2c_versatile_algo;
+	i2c->algo.data = i2c;
+
+	i2c->adap.nr = dev->id;
+	ret = i2c_bit_add_numbered_bus(&i2c->adap);
+	if (ret < 0)
+		return ret;
+
+	platform_set_drvdata(dev, i2c);
+
+	return 0;
+}
+
+static void i2c_versatile_remove(struct platform_device *dev)
+{
+	struct i2c_versatile *i2c = platform_get_drvdata(dev);
+
+	i2c_del_adapter(&i2c->adap);
+}
+
+static const struct of_device_id i2c_versatile_match[] = {
+	{ .compatible = "arm,versatile-i2c", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, i2c_versatile_match);
+
+static struct platform_driver i2c_versatile_driver = {
+	.probe		= i2c_versatile_probe,
+	.remove		= i2c_versatile_remove,
+	.driver		= {
+		.name	= "versatile-i2c",
+		.of_match_table = i2c_versatile_match,
+	},
+};
+
+static int __init i2c_versatile_init(void)
+{
+	return platform_driver_register(&i2c_versatile_driver);
+}
+
+static void __exit i2c_versatile_exit(void)
+{
+	platform_driver_unregister(&i2c_versatile_driver);
+}
+
+subsys_initcall(i2c_versatile_init);
+module_exit(i2c_versatile_exit);
+
+MODULE_DESCRIPTION("ARM Versatile I2C bus driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:versatile-i2c");