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, 90 insertions, 0 deletions

diff --git a/drivers/hwmon/pmbus/mp5920.c b/drivers/hwmon/pmbus/mp5920.c
new file mode 100644
index 000000000..b803f3ddf
--- /dev/null
+++ b/drivers/hwmon/pmbus/mp5920.c
@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Hardware monitoring driver for MP5920 and compatible chips.
+ */
+
+#include <linux/i2c.h>
+#include <linux/minmax.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include "pmbus.h"
+
+static struct pmbus_driver_info mp5920_info = {
+	.pages = 1,
+	.format[PSC_VOLTAGE_IN] = direct,
+	.format[PSC_VOLTAGE_OUT] = direct,
+	.format[PSC_CURRENT_OUT] = direct,
+	.format[PSC_POWER] = direct,
+	.format[PSC_TEMPERATURE] = direct,
+	.m[PSC_VOLTAGE_IN] = 2266,
+	.b[PSC_VOLTAGE_IN] = 0,
+	.R[PSC_VOLTAGE_IN] = -1,
+	.m[PSC_VOLTAGE_OUT] = 2266,
+	.b[PSC_VOLTAGE_OUT] = 0,
+	.R[PSC_VOLTAGE_OUT] = -1,
+	.m[PSC_CURRENT_OUT] = 546,
+	.b[PSC_CURRENT_OUT] = 0,
+	.R[PSC_CURRENT_OUT] = -2,
+	.m[PSC_POWER] = 5840,
+	.b[PSC_POWER] = 0,
+	.R[PSC_POWER] = -3,
+	.m[PSC_TEMPERATURE] = 1067,
+	.b[PSC_TEMPERATURE] = 20500,
+	.R[PSC_TEMPERATURE] = -2,
+	.func[0] = PMBUS_HAVE_VIN  | PMBUS_HAVE_VOUT |
+		PMBUS_HAVE_IOUT | PMBUS_HAVE_POUT |
+		PMBUS_HAVE_TEMP,
+};
+
+static int mp5920_probe(struct i2c_client *client)
+{
+	struct device *dev =  &client->dev;
+	int ret;
+	u8 buf[I2C_SMBUS_BLOCK_MAX];
+
+	if (!i2c_check_functionality(client->adapter,
+				     I2C_FUNC_SMBUS_READ_WORD_DATA))
+		return -ENODEV;
+
+	ret = i2c_smbus_read_block_data(client, PMBUS_MFR_MODEL, buf);
+	if (ret < 0)
+		return dev_err_probe(dev, ret, "Failed to read PMBUS_MFR_MODEL\n");
+
+	if (ret != 6 || strncmp(buf, "MP5920", 6)) {
+		return dev_err_probe(dev, -ENODEV, "Model '%.*s' not supported\n",
+				     min_t(int, ret, sizeof(buf)), buf);
+	}
+
+	return pmbus_do_probe(client, &mp5920_info);
+}
+
+static const struct of_device_id mp5920_of_match[] = {
+	{ .compatible = "mps,mp5920" },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(of, mp5920_of_match);
+
+static const struct i2c_device_id mp5920_id[] = {
+	{ .name = "mp5920" },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(i2c, mp5920_id);
+
+static struct i2c_driver mp5920_driver = {
+	.driver = {
+		.name = "mp5920",
+		.of_match_table = mp5920_of_match,
+	},
+	.probe = mp5920_probe,
+	.id_table = mp5920_id,
+};
+
+module_i2c_driver(mp5920_driver);
+
+MODULE_AUTHOR("Tony Ao <tony_ao@wiwynn.com>");
+MODULE_AUTHOR("Alex Vdovydchenko <xzeol@yahoo.com>");
+MODULE_DESCRIPTION("PMBus driver for MP5920 HSC");
+MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS("PMBUS");