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, 143 insertions, 0 deletions

diff --git a/drivers/mfd/khadas-mcu.c b/drivers/mfd/khadas-mcu.c
new file mode 100644
index 000000000..ba981a788
--- /dev/null
+++ b/drivers/mfd/khadas-mcu.c
@@ -0,0 +1,143 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Driver for Khadas System control Microcontroller
+ *
+ * Copyright (C) 2020 BayLibre SAS
+ *
+ * Author(s): Neil Armstrong <narmstrong@baylibre.com>
+ */
+#include <linux/bitfield.h>
+#include <linux/i2c.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/khadas-mcu.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+
+static bool khadas_mcu_reg_volatile(struct device *dev, unsigned int reg)
+{
+	if (reg >= KHADAS_MCU_USER_DATA_0_REG &&
+	    reg < KHADAS_MCU_PWR_OFF_CMD_REG)
+		return true;
+
+	switch (reg) {
+	case KHADAS_MCU_PWR_OFF_CMD_REG:
+	case KHADAS_MCU_PASSWD_START_REG:
+	case KHADAS_MCU_CHECK_VEN_PASSWD_REG:
+	case KHADAS_MCU_CHECK_USER_PASSWD_REG:
+	case KHADAS_MCU_WOL_INIT_START_REG:
+	case KHADAS_MCU_CMD_FAN_STATUS_CTRL_REG:
+		return true;
+	default:
+		return false;
+	}
+}
+
+static bool khadas_mcu_reg_writeable(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case KHADAS_MCU_PASSWD_VEN_0_REG:
+	case KHADAS_MCU_PASSWD_VEN_1_REG:
+	case KHADAS_MCU_PASSWD_VEN_2_REG:
+	case KHADAS_MCU_PASSWD_VEN_3_REG:
+	case KHADAS_MCU_PASSWD_VEN_4_REG:
+	case KHADAS_MCU_PASSWD_VEN_5_REG:
+	case KHADAS_MCU_MAC_0_REG:
+	case KHADAS_MCU_MAC_1_REG:
+	case KHADAS_MCU_MAC_2_REG:
+	case KHADAS_MCU_MAC_3_REG:
+	case KHADAS_MCU_MAC_4_REG:
+	case KHADAS_MCU_MAC_5_REG:
+	case KHADAS_MCU_USID_0_REG:
+	case KHADAS_MCU_USID_1_REG:
+	case KHADAS_MCU_USID_2_REG:
+	case KHADAS_MCU_USID_3_REG:
+	case KHADAS_MCU_USID_4_REG:
+	case KHADAS_MCU_USID_5_REG:
+	case KHADAS_MCU_VERSION_0_REG:
+	case KHADAS_MCU_VERSION_1_REG:
+	case KHADAS_MCU_DEVICE_NO_0_REG:
+	case KHADAS_MCU_DEVICE_NO_1_REG:
+	case KHADAS_MCU_FACTORY_TEST_REG:
+	case KHADAS_MCU_SHUTDOWN_NORMAL_STATUS_REG:
+		return false;
+	default:
+		return true;
+	}
+}
+
+static const struct regmap_config khadas_mcu_regmap_config = {
+	.reg_bits	= 8,
+	.reg_stride	= 1,
+	.val_bits	= 8,
+	.max_register	= KHADAS_MCU_CMD_FAN_STATUS_CTRL_REG,
+	.volatile_reg	= khadas_mcu_reg_volatile,
+	.writeable_reg	= khadas_mcu_reg_writeable,
+	.cache_type	= REGCACHE_MAPLE,
+};
+
+static struct mfd_cell khadas_mcu_fan_cells[] = {
+	/* VIM1/2 Rev13+ and VIM3 only */
+	{ .name = "khadas-mcu-fan-ctrl", },
+};
+
+static struct mfd_cell khadas_mcu_cells[] = {
+	{ .name = "khadas-mcu-user-mem", },
+};
+
+static int khadas_mcu_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct khadas_mcu *ddata;
+	int ret;
+
+	ddata = devm_kzalloc(dev, sizeof(*ddata), GFP_KERNEL);
+	if (!ddata)
+		return -ENOMEM;
+
+	i2c_set_clientdata(client, ddata);
+
+	ddata->dev = dev;
+
+	ddata->regmap = devm_regmap_init_i2c(client, &khadas_mcu_regmap_config);
+	if (IS_ERR(ddata->regmap)) {
+		ret = PTR_ERR(ddata->regmap);
+		dev_err(dev, "Failed to allocate register map: %d\n", ret);
+		return ret;
+	}
+
+	ret = devm_mfd_add_devices(dev, PLATFORM_DEVID_NONE,
+				   khadas_mcu_cells,
+				   ARRAY_SIZE(khadas_mcu_cells),
+				   NULL, 0, NULL);
+	if (ret)
+		return ret;
+
+	if (of_property_present(dev->of_node, "#cooling-cells"))
+		return devm_mfd_add_devices(dev, PLATFORM_DEVID_NONE,
+					    khadas_mcu_fan_cells,
+					    ARRAY_SIZE(khadas_mcu_fan_cells),
+					    NULL, 0, NULL);
+
+	return 0;
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id khadas_mcu_of_match[] = {
+	{ .compatible = "khadas,mcu", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, khadas_mcu_of_match);
+#endif
+
+static struct i2c_driver khadas_mcu_driver = {
+	.driver = {
+		.name = "khadas-mcu-core",
+		.of_match_table = of_match_ptr(khadas_mcu_of_match),
+	},
+	.probe = khadas_mcu_probe,
+};
+module_i2c_driver(khadas_mcu_driver);
+
+MODULE_DESCRIPTION("Khadas MCU core driver");
+MODULE_AUTHOR("Neil Armstrong <narmstrong@baylibre.com>");
+MODULE_LICENSE("GPL v2");