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, 399 insertions, 0 deletions

diff --git a/drivers/hwmon/max1619.c b/drivers/hwmon/max1619.c
new file mode 100644
index 000000000..77ef39e8a
--- /dev/null
+++ b/drivers/hwmon/max1619.c
@@ -0,0 +1,399 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * max1619.c - Part of lm_sensors, Linux kernel modules for hardware
+ *             monitoring
+ * Copyright (C) 2003-2004 Oleksij Rempel <bug-track@fisher-privat.net>
+ *                         Jean Delvare <jdelvare@suse.de>
+ *
+ * Based on the lm90 driver. The MAX1619 is a sensor chip made by Maxim.
+ * It reports up to two temperatures (its own plus up to
+ * one external one). Complete datasheet can be
+ * obtained from Maxim's website at:
+ *   http://pdfserv.maxim-ic.com/en/ds/MAX1619.pdf
+ */
+
+#include <linux/err.h>
+#include <linux/hwmon.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+#include <linux/util_macros.h>
+
+static const unsigned short normal_i2c[] = {
+	0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b, 0x4c, 0x4d, 0x4e, I2C_CLIENT_END };
+
+#define MAX1619_REG_LOCAL_TEMP		0x00
+#define MAX1619_REG_REMOTE_TEMP		0x01
+#define MAX1619_REG_STATUS		0x02
+#define MAX1619_REG_CONFIG		0x03
+#define MAX1619_REG_CONVRATE		0x04
+#define MAX1619_REG_REMOTE_HIGH		0x07
+#define MAX1619_REG_REMOTE_LOW		0x08
+#define MAX1619_REG_REMOTE_CRIT		0x10
+#define MAX1619_REG_REMOTE_CRIT_HYST	0x11
+#define MAX1619_REG_MAN_ID		0xFE
+#define MAX1619_REG_CHIP_ID		0xFF
+
+static int get_alarms(struct regmap *regmap)
+{
+	static u32 regs[2] = { MAX1619_REG_STATUS, MAX1619_REG_CONFIG };
+	u8 regdata[2];
+	int ret;
+
+	ret = regmap_multi_reg_read(regmap, regs, regdata, 2);
+	if (ret)
+		return ret;
+
+	/* OVERT status bit may be reversed */
+	if (!(regdata[1] & 0x20))
+		regdata[0] ^= 0x02;
+
+	return regdata[0] & 0x1e;
+}
+
+static int max1619_temp_read(struct regmap *regmap, u32 attr, int channel, long *val)
+{
+	int reg = -1, alarm_bit = 0;
+	u32 temp;
+	int ret;
+
+	switch (attr) {
+	case hwmon_temp_input:
+		reg = channel ? MAX1619_REG_REMOTE_TEMP : MAX1619_REG_LOCAL_TEMP;
+		break;
+	case hwmon_temp_min:
+		reg = MAX1619_REG_REMOTE_LOW;
+		break;
+	case hwmon_temp_max:
+		reg = MAX1619_REG_REMOTE_HIGH;
+		break;
+	case hwmon_temp_crit:
+		reg = MAX1619_REG_REMOTE_CRIT;
+		break;
+	case hwmon_temp_crit_hyst:
+		reg = MAX1619_REG_REMOTE_CRIT_HYST;
+		break;
+	case hwmon_temp_min_alarm:
+		alarm_bit = 3;
+		break;
+	case hwmon_temp_max_alarm:
+		alarm_bit = 4;
+		break;
+	case hwmon_temp_crit_alarm:
+		alarm_bit = 1;
+		break;
+	case hwmon_temp_fault:
+		alarm_bit = 2;
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+	if (reg >= 0) {
+		ret = regmap_read(regmap, reg, &temp);
+		if (ret < 0)
+			return ret;
+		*val = sign_extend32(temp, 7) * 1000;
+	} else {
+		ret = get_alarms(regmap);
+		if (ret < 0)
+			return ret;
+		*val = !!(ret & BIT(alarm_bit));
+	}
+	return 0;
+}
+
+static u16 update_intervals[] = { 16000, 8000, 4000, 2000, 1000, 500, 250, 125 };
+
+static int max1619_chip_read(struct regmap *regmap, u32 attr, long *val)
+{
+	int alarms, ret;
+	u32 regval;
+
+	switch (attr) {
+	case hwmon_chip_update_interval:
+		ret = regmap_read(regmap, MAX1619_REG_CONVRATE, &regval);
+		if (ret < 0)
+			return ret;
+		*val = update_intervals[regval & 7];
+		break;
+	case hwmon_chip_alarms:
+		alarms = get_alarms(regmap);
+		if (alarms < 0)
+			return alarms;
+		*val = alarms;
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+	return 0;
+}
+
+static int max1619_read(struct device *dev, enum hwmon_sensor_types type,
+			u32 attr, int channel, long *val)
+{
+	struct regmap *regmap = dev_get_drvdata(dev);
+
+	switch (type) {
+	case hwmon_chip:
+		return max1619_chip_read(regmap, attr, val);
+	case hwmon_temp:
+		return max1619_temp_read(regmap, attr, channel, val);
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
+static int max1619_chip_write(struct regmap *regmap, u32 attr, long val)
+{
+	switch (attr) {
+	case hwmon_chip_update_interval:
+		val = find_closest_descending(val, update_intervals, ARRAY_SIZE(update_intervals));
+		return regmap_write(regmap, MAX1619_REG_CONVRATE, val);
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
+static int max1619_temp_write(struct regmap *regmap,
+			      u32 attr, int channel, long val)
+{
+	int reg;
+
+	switch (attr) {
+	case hwmon_temp_min:
+		reg = MAX1619_REG_REMOTE_LOW;
+		break;
+	case hwmon_temp_max:
+		reg = MAX1619_REG_REMOTE_HIGH;
+		break;
+	case hwmon_temp_crit:
+		reg = MAX1619_REG_REMOTE_CRIT;
+		break;
+	case hwmon_temp_crit_hyst:
+		reg = MAX1619_REG_REMOTE_CRIT_HYST;
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+	val = DIV_ROUND_CLOSEST(clamp_val(val, -128000, 127000), 1000);
+	return regmap_write(regmap, reg, val);
+}
+
+static int max1619_write(struct device *dev, enum hwmon_sensor_types type,
+			 u32 attr, int channel, long val)
+{
+	struct regmap *regmap = dev_get_drvdata(dev);
+
+	switch (type) {
+	case hwmon_chip:
+		return max1619_chip_write(regmap, attr, val);
+	case hwmon_temp:
+		return max1619_temp_write(regmap, attr, channel, val);
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
+static umode_t max1619_is_visible(const void *_data, enum hwmon_sensor_types type,
+				  u32 attr, int channel)
+{
+	switch (type) {
+	case hwmon_chip:
+		switch (attr) {
+		case hwmon_chip_update_interval:
+			return 0644;
+		case hwmon_chip_alarms:
+			return 0444;
+		default:
+			break;
+		}
+		break;
+	case hwmon_temp:
+		switch (attr) {
+		case hwmon_temp_input:
+			return 0444;
+		case hwmon_temp_min:
+		case hwmon_temp_max:
+		case hwmon_temp_crit:
+		case hwmon_temp_crit_hyst:
+			return 0644;
+		case hwmon_temp_min_alarm:
+		case hwmon_temp_max_alarm:
+		case hwmon_temp_crit_alarm:
+		case hwmon_temp_fault:
+			return 0444;
+		default:
+			break;
+		}
+		break;
+	default:
+		break;
+	}
+	return 0;
+}
+
+static const struct hwmon_channel_info * const max1619_info[] = {
+	HWMON_CHANNEL_INFO(chip, HWMON_C_ALARMS | HWMON_C_UPDATE_INTERVAL),
+	HWMON_CHANNEL_INFO(temp,
+			   HWMON_T_INPUT,
+			   HWMON_T_INPUT | HWMON_T_MIN | HWMON_T_MAX |
+			   HWMON_T_CRIT | HWMON_T_CRIT_HYST |
+			   HWMON_T_MIN_ALARM | HWMON_T_MAX_ALARM |
+			   HWMON_T_CRIT_ALARM | HWMON_T_FAULT),
+	NULL
+};
+
+static const struct hwmon_ops max1619_hwmon_ops = {
+	.is_visible = max1619_is_visible,
+	.read = max1619_read,
+	.write = max1619_write,
+};
+
+static const struct hwmon_chip_info max1619_chip_info = {
+	.ops = &max1619_hwmon_ops,
+	.info = max1619_info,
+};
+
+/* Return 0 if detection is successful, -ENODEV otherwise */
+static int max1619_detect(struct i2c_client *client,
+			  struct i2c_board_info *info)
+{
+	struct i2c_adapter *adapter = client->adapter;
+	int regval;
+
+	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
+		return -ENODEV;
+
+	regval = i2c_smbus_read_byte_data(client, MAX1619_REG_CONFIG);
+	if (regval < 0 || (regval & 0x03))
+		return -ENODEV;
+	regval = i2c_smbus_read_byte_data(client, MAX1619_REG_CONVRATE);
+	if (regval < 0 || regval > 0x07)
+		return -ENODEV;
+	regval = i2c_smbus_read_byte_data(client, MAX1619_REG_STATUS);
+	if (regval < 0 || (regval & 0x61))
+		return -ENODEV;
+
+	regval = i2c_smbus_read_byte_data(client, MAX1619_REG_MAN_ID);
+	if (regval != 0x4d)
+		return -ENODEV;
+	regval = i2c_smbus_read_byte_data(client, MAX1619_REG_CHIP_ID);
+	if (regval != 0x04)
+		return -ENODEV;
+
+	strscpy(info->type, "max1619", I2C_NAME_SIZE);
+
+	return 0;
+}
+
+static int max1619_init_chip(struct regmap *regmap)
+{
+	int ret;
+
+	ret = regmap_write(regmap, MAX1619_REG_CONVRATE, 5);	/* 2 Hz */
+	if (ret)
+		return ret;
+
+	/* Start conversions */
+	return regmap_clear_bits(regmap, MAX1619_REG_CONFIG, 0x40);
+}
+
+/* regmap */
+
+static int max1619_reg_read(void *context, unsigned int reg, unsigned int *val)
+{
+	int ret;
+
+	ret = i2c_smbus_read_byte_data(context, reg);
+	if (ret < 0)
+		return ret;
+
+	*val = ret;
+	return 0;
+}
+
+static int max1619_reg_write(void *context, unsigned int reg, unsigned int val)
+{
+	int offset = reg < MAX1619_REG_REMOTE_CRIT ? 6 : 2;
+
+	return i2c_smbus_write_byte_data(context, reg + offset, val);
+}
+
+static bool max1619_regmap_is_volatile(struct device *dev, unsigned int reg)
+{
+	return reg <= MAX1619_REG_STATUS;
+}
+
+static bool max1619_regmap_is_writeable(struct device *dev, unsigned int reg)
+{
+	return reg > MAX1619_REG_STATUS && reg <= MAX1619_REG_REMOTE_CRIT_HYST;
+}
+
+static const struct regmap_config max1619_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = MAX1619_REG_REMOTE_CRIT_HYST,
+	.cache_type = REGCACHE_MAPLE,
+	.volatile_reg = max1619_regmap_is_volatile,
+	.writeable_reg = max1619_regmap_is_writeable,
+};
+
+static const struct regmap_bus max1619_regmap_bus = {
+	.reg_write = max1619_reg_write,
+	.reg_read = max1619_reg_read,
+};
+
+static int max1619_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct device *hwmon_dev;
+	struct regmap *regmap;
+	int ret;
+
+	regmap = devm_regmap_init(dev, &max1619_regmap_bus, client,
+				  &max1619_regmap_config);
+	if (IS_ERR(regmap))
+		return PTR_ERR(regmap);
+
+	ret = max1619_init_chip(regmap);
+	if (ret)
+		return ret;
+
+	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name,
+							 regmap, &max1619_chip_info, NULL);
+	return PTR_ERR_OR_ZERO(hwmon_dev);
+}
+
+static const struct i2c_device_id max1619_id[] = {
+	{ .name = "max1619" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, max1619_id);
+
+#ifdef CONFIG_OF
+static const struct of_device_id max1619_of_match[] = {
+	{ .compatible = "maxim,max1619", },
+	{},
+};
+
+MODULE_DEVICE_TABLE(of, max1619_of_match);
+#endif
+
+static struct i2c_driver max1619_driver = {
+	.class		= I2C_CLASS_HWMON,
+	.driver = {
+		.name	= "max1619",
+		.of_match_table = of_match_ptr(max1619_of_match),
+	},
+	.probe		= max1619_probe,
+	.id_table	= max1619_id,
+	.detect		= max1619_detect,
+	.address_list	= normal_i2c,
+};
+
+module_i2c_driver(max1619_driver);
+
+MODULE_AUTHOR("Oleksij Rempel <bug-track@fisher-privat.net>, Jean Delvare <jdelvare@suse.de>");
+MODULE_DESCRIPTION("MAX1619 sensor driver");
+MODULE_LICENSE("GPL");