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, 213 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-sd3078.c b/drivers/rtc/rtc-sd3078.c
new file mode 100644
index 000000000..2c61f0e20
--- /dev/null
+++ b/drivers/rtc/rtc-sd3078.c
@@ -0,0 +1,213 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Real Time Clock (RTC) Driver for sd3078
+ * Copyright (C) 2018 Zoro Li
+ */
+
+#include <linux/bcd.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+#include <linux/rtc.h>
+#include <linux/slab.h>
+
+#define SD3078_REG_SC			0x00
+#define SD3078_REG_MN			0x01
+#define SD3078_REG_HR			0x02
+#define SD3078_REG_DW			0x03
+#define SD3078_REG_DM			0x04
+#define SD3078_REG_MO			0x05
+#define SD3078_REG_YR			0x06
+
+#define SD3078_REG_CTRL1		0x0f
+#define SD3078_REG_CTRL2		0x10
+#define SD3078_REG_CTRL3		0x11
+
+#define KEY_WRITE1		0x80
+#define KEY_WRITE2		0x04
+#define KEY_WRITE3		0x80
+
+#define NUM_TIME_REGS   (SD3078_REG_YR - SD3078_REG_SC + 1)
+
+/*
+ * The sd3078 has write protection
+ * and we can choose whether or not to use it.
+ * Write protection is turned off by default.
+ */
+#define WRITE_PROTECT_EN	0
+
+/*
+ * In order to prevent arbitrary modification of the time register,
+ * when modification of the register,
+ * the "write" bit needs to be written in a certain order.
+ * 1. set WRITE1 bit
+ * 2. set WRITE2 bit
+ * 3. set WRITE3 bit
+ */
+static void sd3078_enable_reg_write(struct regmap *regmap)
+{
+	regmap_update_bits(regmap, SD3078_REG_CTRL2, KEY_WRITE1, KEY_WRITE1);
+	regmap_update_bits(regmap, SD3078_REG_CTRL1, KEY_WRITE2, KEY_WRITE2);
+	regmap_update_bits(regmap, SD3078_REG_CTRL1, KEY_WRITE3, KEY_WRITE3);
+}
+
+#if WRITE_PROTECT_EN
+/*
+ * In order to prevent arbitrary modification of the time register,
+ * we should disable the write function.
+ * when disable write,
+ * the "write" bit needs to be clear in a certain order.
+ * 1. clear WRITE2 bit
+ * 2. clear WRITE3 bit
+ * 3. clear WRITE1 bit
+ */
+static void sd3078_disable_reg_write(struct regmap *regmap)
+{
+	regmap_update_bits(regmap, SD3078_REG_CTRL1, KEY_WRITE2, 0);
+	regmap_update_bits(regmap, SD3078_REG_CTRL1, KEY_WRITE3, 0);
+	regmap_update_bits(regmap, SD3078_REG_CTRL2, KEY_WRITE1, 0);
+}
+#endif
+
+static int sd3078_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	unsigned char hour;
+	unsigned char rtc_data[NUM_TIME_REGS] = {0};
+	struct i2c_client *client = to_i2c_client(dev);
+	struct regmap *regmap = i2c_get_clientdata(client);
+	int ret;
+
+	ret = regmap_bulk_read(regmap, SD3078_REG_SC, rtc_data, NUM_TIME_REGS);
+	if (ret < 0) {
+		dev_err(dev, "reading from RTC failed with err:%d\n", ret);
+		return ret;
+	}
+
+	tm->tm_sec	= bcd2bin(rtc_data[SD3078_REG_SC] & 0x7F);
+	tm->tm_min	= bcd2bin(rtc_data[SD3078_REG_MN] & 0x7F);
+
+	/*
+	 * The sd3078 supports 12/24 hour mode.
+	 * When getting time,
+	 * we need to convert the 12 hour mode to the 24 hour mode.
+	 */
+	hour = rtc_data[SD3078_REG_HR];
+	if (hour & 0x80) /* 24H MODE */
+		tm->tm_hour = bcd2bin(rtc_data[SD3078_REG_HR] & 0x3F);
+	else if (hour & 0x20) /* 12H MODE PM */
+		tm->tm_hour = bcd2bin(rtc_data[SD3078_REG_HR] & 0x1F) + 12;
+	else /* 12H MODE AM */
+		tm->tm_hour = bcd2bin(rtc_data[SD3078_REG_HR] & 0x1F);
+
+	tm->tm_mday = bcd2bin(rtc_data[SD3078_REG_DM] & 0x3F);
+	tm->tm_wday = rtc_data[SD3078_REG_DW] & 0x07;
+	tm->tm_mon	= bcd2bin(rtc_data[SD3078_REG_MO] & 0x1F) - 1;
+	tm->tm_year = bcd2bin(rtc_data[SD3078_REG_YR]) + 100;
+
+	return 0;
+}
+
+static int sd3078_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	unsigned char rtc_data[NUM_TIME_REGS];
+	struct i2c_client *client = to_i2c_client(dev);
+	struct regmap *regmap = i2c_get_clientdata(client);
+	int ret;
+
+	rtc_data[SD3078_REG_SC] = bin2bcd(tm->tm_sec);
+	rtc_data[SD3078_REG_MN] = bin2bcd(tm->tm_min);
+	rtc_data[SD3078_REG_HR] = bin2bcd(tm->tm_hour) | 0x80;
+	rtc_data[SD3078_REG_DM] = bin2bcd(tm->tm_mday);
+	rtc_data[SD3078_REG_DW] = tm->tm_wday & 0x07;
+	rtc_data[SD3078_REG_MO] = bin2bcd(tm->tm_mon) + 1;
+	rtc_data[SD3078_REG_YR] = bin2bcd(tm->tm_year - 100);
+
+#if WRITE_PROTECT_EN
+	sd3078_enable_reg_write(regmap);
+#endif
+
+	ret = regmap_bulk_write(regmap, SD3078_REG_SC, rtc_data,
+				NUM_TIME_REGS);
+	if (ret < 0) {
+		dev_err(dev, "writing to RTC failed with err:%d\n", ret);
+		return ret;
+	}
+
+#if WRITE_PROTECT_EN
+	sd3078_disable_reg_write(regmap);
+#endif
+
+	return 0;
+}
+
+static const struct rtc_class_ops sd3078_rtc_ops = {
+	.read_time	= sd3078_rtc_read_time,
+	.set_time	= sd3078_rtc_set_time,
+};
+
+static const struct regmap_config regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = 0x11,
+};
+
+static int sd3078_probe(struct i2c_client *client)
+{
+	int ret;
+	struct regmap *regmap;
+	struct rtc_device *rtc;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+		return -ENODEV;
+
+	regmap = devm_regmap_init_i2c(client, &regmap_config);
+	if (IS_ERR(regmap)) {
+		dev_err(&client->dev, "regmap allocation failed\n");
+		return PTR_ERR(regmap);
+	}
+
+	i2c_set_clientdata(client, regmap);
+
+	rtc = devm_rtc_allocate_device(&client->dev);
+	if (IS_ERR(rtc))
+		return PTR_ERR(rtc);
+
+	rtc->ops = &sd3078_rtc_ops;
+	rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
+	rtc->range_max = RTC_TIMESTAMP_END_2099;
+
+	ret = devm_rtc_register_device(rtc);
+	if (ret)
+		return ret;
+
+	sd3078_enable_reg_write(regmap);
+
+	return 0;
+}
+
+static const struct i2c_device_id sd3078_id[] = {
+	{ .name = "sd3078" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, sd3078_id);
+
+static const __maybe_unused struct of_device_id rtc_dt_match[] = {
+	{ .compatible = "whwave,sd3078" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, rtc_dt_match);
+
+static struct i2c_driver sd3078_driver = {
+	.driver     = {
+		.name   = "sd3078",
+		.of_match_table = of_match_ptr(rtc_dt_match),
+	},
+	.probe      = sd3078_probe,
+	.id_table   = sd3078_id,
+};
+
+module_i2c_driver(sd3078_driver);
+
+MODULE_AUTHOR("Dianlong Li <long17.cool@163.com>");
+MODULE_DESCRIPTION("SD3078 RTC driver");
+MODULE_LICENSE("GPL v2");