x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

When using eBPF to probe CS CALL instructions within a function,
a crash can be triggered.

The eBPF tool probes offset 257 of the __hrtimer_run_queues()
function:

<__hrtimer_run_queues+249>:  nopl   0x0(%rax,%rax,1)
<__hrtimer_run_queues+254>:  mov    %r14,%rdi
<__hrtimer_run_queues+257>:  cs call <__x86_indirect_thunk_r12>
<__hrtimer_run_queues+263>:  mov    %eax,%r12d
<__hrtimer_run_queues+266>:  xchg   %ax,%ax
<__hrtimer_run_queues+268>:  mov    %r13,%rdi

Which triggers this crash:

  BUG: unable to handle page fault for address: 00000000000f41c9
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: 0002 [#1] SMP NOPTI
  CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P
  RIP: 0010:__hrtimer_run_queues+0x106/0x230

Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is
at the 6th byte of the above CS CALL instruction. Since the CS CALL
instruction occupies 6 bytes, the exception occurred in the middle of that
call instruction.

The root cause is that when using eBPF tools to probe in the middle of a
function, a kprobe with INT3 is used as the underlying implementation.

During single-step emulation of the original CALL instruction,
int3_emulate_call() assumes that the probed CALL instruction is 5 bytes
long. However, the actual CS-prefixed CALL instruction occupies 6 bytes,
so it constructs an incorrect exception return address. When the CPU
returns from the kprobe handler, the next instruction to be executed is at
the address of the last byte of that CS CALL instruction. Coincidentally,
starting from that address, the CPU fetches and decodes a completely
different instruction, which ultimately triggers a kernel crash.

Fix the issue by using the actual instruction length obtained from
the instruction decoder when constructing the exception return
address, rather than relying on the hardcoded CALL_INSN_SIZE macro.

[ mingo: Refined the changelog ]

Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step")
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

1 files changed, 234 insertions, 0 deletions

diff --git a/drivers/hwmon/ad7414.c b/drivers/hwmon/ad7414.c
new file mode 100644
index 000000000..c2df631ae
--- /dev/null
+++ b/drivers/hwmon/ad7414.c
@@ -0,0 +1,234 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * An hwmon driver for the Analog Devices AD7414
+ *
+ * Copyright 2006 Stefan Roese <sr at denx.de>, DENX Software Engineering
+ *
+ * Copyright (c) 2008 PIKA Technologies
+ *   Sean MacLennan <smaclennan@pikatech.com>
+ *
+ * Copyright (c) 2008 Spansion Inc.
+ *   Frank Edelhaeuser <frank.edelhaeuser at spansion.com>
+ *   (converted to "new style" I2C driver model, removed checkpatch.pl warnings)
+ *
+ * Based on ad7418.c
+ * Copyright 2006 Tower Technologies, Alessandro Zummo <a.zummo at towertech.it>
+ */
+
+#include <linux/module.h>
+#include <linux/jiffies.h>
+#include <linux/i2c.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/err.h>
+#include <linux/mutex.h>
+#include <linux/sysfs.h>
+#include <linux/slab.h>
+
+
+/* AD7414 registers */
+#define AD7414_REG_TEMP		0x00
+#define AD7414_REG_CONF		0x01
+#define AD7414_REG_T_HIGH	0x02
+#define AD7414_REG_T_LOW	0x03
+
+static u8 AD7414_REG_LIMIT[] = { AD7414_REG_T_HIGH, AD7414_REG_T_LOW };
+
+struct ad7414_data {
+	struct i2c_client	*client;
+	struct mutex		lock;	/* atomic read data updates */
+	bool			valid;	/* true if following fields are valid */
+	unsigned long		next_update;	/* In jiffies */
+	s16			temp_input;	/* Register values */
+	s8			temps[ARRAY_SIZE(AD7414_REG_LIMIT)];
+};
+
+/* REG: (0.25C/bit, two's complement) << 6 */
+static inline int ad7414_temp_from_reg(s16 reg)
+{
+	/*
+	 * use integer division instead of equivalent right shift to
+	 * guarantee arithmetic shift and preserve the sign
+	 */
+	return ((int)reg / 64) * 250;
+}
+
+static inline int ad7414_read(struct i2c_client *client, u8 reg)
+{
+	if (reg == AD7414_REG_TEMP)
+		return i2c_smbus_read_word_swapped(client, reg);
+	else
+		return i2c_smbus_read_byte_data(client, reg);
+}
+
+static inline int ad7414_write(struct i2c_client *client, u8 reg, u8 value)
+{
+	return i2c_smbus_write_byte_data(client, reg, value);
+}
+
+static struct ad7414_data *ad7414_update_device(struct device *dev)
+{
+	struct ad7414_data *data = dev_get_drvdata(dev);
+	struct i2c_client *client = data->client;
+
+	mutex_lock(&data->lock);
+
+	if (time_after(jiffies, data->next_update) || !data->valid) {
+		int value, i;
+
+		dev_dbg(&client->dev, "starting ad7414 update\n");
+
+		value = ad7414_read(client, AD7414_REG_TEMP);
+		if (value < 0)
+			dev_dbg(&client->dev, "AD7414_REG_TEMP err %d\n",
+				value);
+		else
+			data->temp_input = value;
+
+		for (i = 0; i < ARRAY_SIZE(AD7414_REG_LIMIT); ++i) {
+			value = ad7414_read(client, AD7414_REG_LIMIT[i]);
+			if (value < 0)
+				dev_dbg(&client->dev, "AD7414 reg %d err %d\n",
+					AD7414_REG_LIMIT[i], value);
+			else
+				data->temps[i] = value;
+		}
+
+		data->next_update = jiffies + HZ + HZ / 2;
+		data->valid = true;
+	}
+
+	mutex_unlock(&data->lock);
+
+	return data;
+}
+
+static ssize_t temp_input_show(struct device *dev,
+			       struct device_attribute *attr, char *buf)
+{
+	struct ad7414_data *data = ad7414_update_device(dev);
+	return sprintf(buf, "%d\n", ad7414_temp_from_reg(data->temp_input));
+}
+static SENSOR_DEVICE_ATTR_RO(temp1_input, temp_input, 0);
+
+static ssize_t max_min_show(struct device *dev, struct device_attribute *attr,
+			    char *buf)
+{
+	int index = to_sensor_dev_attr(attr)->index;
+	struct ad7414_data *data = ad7414_update_device(dev);
+	return sprintf(buf, "%d\n", data->temps[index] * 1000);
+}
+
+static ssize_t max_min_store(struct device *dev,
+			     struct device_attribute *attr, const char *buf,
+			     size_t count)
+{
+	struct ad7414_data *data = dev_get_drvdata(dev);
+	struct i2c_client *client = data->client;
+	int index = to_sensor_dev_attr(attr)->index;
+	u8 reg = AD7414_REG_LIMIT[index];
+	long temp;
+	int ret = kstrtol(buf, 10, &temp);
+
+	if (ret < 0)
+		return ret;
+
+	temp = clamp_val(temp, -40000, 85000);
+	temp = (temp + (temp < 0 ? -500 : 500)) / 1000;
+
+	mutex_lock(&data->lock);
+	data->temps[index] = temp;
+	ad7414_write(client, reg, temp);
+	mutex_unlock(&data->lock);
+	return count;
+}
+
+static SENSOR_DEVICE_ATTR_RW(temp1_max, max_min, 0);
+static SENSOR_DEVICE_ATTR_RW(temp1_min, max_min, 1);
+
+static ssize_t alarm_show(struct device *dev, struct device_attribute *attr,
+			  char *buf)
+{
+	int bitnr = to_sensor_dev_attr(attr)->index;
+	struct ad7414_data *data = ad7414_update_device(dev);
+	int value = (data->temp_input >> bitnr) & 1;
+	return sprintf(buf, "%d\n", value);
+}
+
+static SENSOR_DEVICE_ATTR_RO(temp1_min_alarm, alarm, 3);
+static SENSOR_DEVICE_ATTR_RO(temp1_max_alarm, alarm, 4);
+
+static struct attribute *ad7414_attrs[] = {
+	&sensor_dev_attr_temp1_input.dev_attr.attr,
+	&sensor_dev_attr_temp1_max.dev_attr.attr,
+	&sensor_dev_attr_temp1_min.dev_attr.attr,
+	&sensor_dev_attr_temp1_max_alarm.dev_attr.attr,
+	&sensor_dev_attr_temp1_min_alarm.dev_attr.attr,
+	NULL
+};
+
+ATTRIBUTE_GROUPS(ad7414);
+
+static int ad7414_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct ad7414_data *data;
+	struct device *hwmon_dev;
+	int conf;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_BYTE_DATA |
+				     I2C_FUNC_SMBUS_READ_WORD_DATA))
+		return -EOPNOTSUPP;
+
+	data = devm_kzalloc(dev, sizeof(struct ad7414_data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->client = client;
+	mutex_init(&data->lock);
+
+	dev_info(&client->dev, "chip found\n");
+
+	/* Make sure the chip is powered up. */
+	conf = i2c_smbus_read_byte_data(client, AD7414_REG_CONF);
+	if (conf < 0)
+		dev_warn(dev, "ad7414_probe unable to read config register.\n");
+	else {
+		conf &= ~(1 << 7);
+		i2c_smbus_write_byte_data(client, AD7414_REG_CONF, conf);
+	}
+
+	hwmon_dev = devm_hwmon_device_register_with_groups(dev,
+							   client->name,
+							   data, ad7414_groups);
+	return PTR_ERR_OR_ZERO(hwmon_dev);
+}
+
+static const struct i2c_device_id ad7414_id[] = {
+	{ .name = "ad7414" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, ad7414_id);
+
+static const struct of_device_id __maybe_unused ad7414_of_match[] = {
+	{ .compatible = "ad,ad7414" },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, ad7414_of_match);
+
+static struct i2c_driver ad7414_driver = {
+	.driver = {
+		.name	= "ad7414",
+		.of_match_table = of_match_ptr(ad7414_of_match),
+	},
+	.probe = ad7414_probe,
+	.id_table = ad7414_id,
+};
+
+module_i2c_driver(ad7414_driver);
+
+MODULE_AUTHOR("Stefan Roese <sr at denx.de>, "
+	      "Frank Edelhaeuser <frank.edelhaeuser at spansion.com>");
+
+MODULE_DESCRIPTION("AD7414 driver");
+MODULE_LICENSE("GPL");