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, 216 insertions, 0 deletions

diff --git a/drivers/hwmon/ltc4151.c b/drivers/hwmon/ltc4151.c
new file mode 100644
index 000000000..fa7c57aae
--- /dev/null
+++ b/drivers/hwmon/ltc4151.c
@@ -0,0 +1,216 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Driver for Linear Technology LTC4151 High Voltage I2C Current
+ * and Voltage Monitor
+ *
+ * Copyright (C) 2011 AppearTV AS
+ *
+ * Derived from:
+ *
+ *  Driver for Linear Technology LTC4261 I2C Negative Voltage Hot
+ *  Swap Controller
+ *  Copyright (C) 2010 Ericsson AB.
+ *
+ * Datasheet: http://www.linear.com/docs/Datasheet/4151fc.pdf
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/init.h>
+#include <linux/err.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/jiffies.h>
+
+/* chip registers */
+#define LTC4151_SENSE_H	0x00
+#define LTC4151_SENSE_L	0x01
+#define LTC4151_VIN_H	0x02
+#define LTC4151_VIN_L	0x03
+#define LTC4151_ADIN_H	0x04
+#define LTC4151_ADIN_L	0x05
+
+struct ltc4151_data {
+	struct i2c_client *client;
+
+	struct mutex update_lock;
+	bool valid;
+	unsigned long last_updated; /* in jiffies */
+	unsigned int shunt; /* in micro ohms */
+
+	/* Registers */
+	u8 regs[6];
+};
+
+static struct ltc4151_data *ltc4151_update_device(struct device *dev)
+{
+	struct ltc4151_data *data = dev_get_drvdata(dev);
+	struct i2c_client *client = data->client;
+	struct ltc4151_data *ret = data;
+
+	mutex_lock(&data->update_lock);
+
+	/*
+	 * The chip's A/D updates 6 times per second
+	 * (Conversion Rate 6 - 9 Hz)
+	 */
+	if (time_after(jiffies, data->last_updated + HZ / 6) || !data->valid) {
+		int i;
+
+		dev_dbg(&client->dev, "Starting ltc4151 update\n");
+
+		/* Read all registers */
+		for (i = 0; i < ARRAY_SIZE(data->regs); i++) {
+			int val;
+
+			val = i2c_smbus_read_byte_data(client, i);
+			if (unlikely(val < 0)) {
+				dev_dbg(dev,
+					"Failed to read ADC value: error %d\n",
+					val);
+				ret = ERR_PTR(val);
+				goto abort;
+			}
+			data->regs[i] = val;
+		}
+		data->last_updated = jiffies;
+		data->valid = true;
+	}
+abort:
+	mutex_unlock(&data->update_lock);
+	return ret;
+}
+
+/* Return the voltage from the given register in mV */
+static int ltc4151_get_value(struct ltc4151_data *data, u8 reg)
+{
+	u32 val;
+
+	val = (data->regs[reg] << 4) + (data->regs[reg + 1] >> 4);
+
+	switch (reg) {
+	case LTC4151_ADIN_H:
+		/* 500uV resolution. Convert to mV. */
+		val = val * 500 / 1000;
+		break;
+	case LTC4151_SENSE_H:
+		/*
+		 * 20uV resolution. Convert to current as measured with
+		 * a given sense resistor, in mA.
+		 */
+		val = val * 20 * 1000 / data->shunt;
+		break;
+	case LTC4151_VIN_H:
+		/* 25 mV per increment */
+		val = val * 25;
+		break;
+	default:
+		/* If we get here, the developer messed up */
+		WARN_ON_ONCE(1);
+		val = 0;
+		break;
+	}
+
+	return val;
+}
+
+static ssize_t ltc4151_value_show(struct device *dev,
+				  struct device_attribute *da, char *buf)
+{
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
+	struct ltc4151_data *data = ltc4151_update_device(dev);
+	int value;
+
+	if (IS_ERR(data))
+		return PTR_ERR(data);
+
+	value = ltc4151_get_value(data, attr->index);
+	return sysfs_emit(buf, "%d\n", value);
+}
+
+/*
+ * Input voltages.
+ */
+static SENSOR_DEVICE_ATTR_RO(in1_input, ltc4151_value, LTC4151_VIN_H);
+static SENSOR_DEVICE_ATTR_RO(in2_input, ltc4151_value, LTC4151_ADIN_H);
+
+/* Currents (via sense resistor) */
+static SENSOR_DEVICE_ATTR_RO(curr1_input, ltc4151_value, LTC4151_SENSE_H);
+
+/*
+ * Finally, construct an array of pointers to members of the above objects,
+ * as required for sysfs_create_group()
+ */
+static struct attribute *ltc4151_attrs[] = {
+	&sensor_dev_attr_in1_input.dev_attr.attr,
+	&sensor_dev_attr_in2_input.dev_attr.attr,
+
+	&sensor_dev_attr_curr1_input.dev_attr.attr,
+
+	NULL,
+};
+ATTRIBUTE_GROUPS(ltc4151);
+
+static int ltc4151_probe(struct i2c_client *client)
+{
+	struct i2c_adapter *adapter = client->adapter;
+	struct device *dev = &client->dev;
+	struct ltc4151_data *data;
+	struct device *hwmon_dev;
+	u32 shunt;
+
+	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
+		return -ENODEV;
+
+	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	if (of_property_read_u32(client->dev.of_node,
+				 "shunt-resistor-micro-ohms", &shunt))
+		shunt = 1000; /* 1 mOhm if not set via DT */
+
+	if (shunt == 0)
+		return -EINVAL;
+
+	data->shunt = shunt;
+
+	data->client = client;
+	mutex_init(&data->update_lock);
+
+	hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
+							   data,
+							   ltc4151_groups);
+	return PTR_ERR_OR_ZERO(hwmon_dev);
+}
+
+static const struct i2c_device_id ltc4151_id[] = {
+	{ .name = "ltc4151" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, ltc4151_id);
+
+static const struct of_device_id __maybe_unused ltc4151_match[] = {
+	{ .compatible = "lltc,ltc4151" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, ltc4151_match);
+
+/* This is the driver that will be inserted */
+static struct i2c_driver ltc4151_driver = {
+	.driver = {
+		.name	= "ltc4151",
+		.of_match_table = of_match_ptr(ltc4151_match),
+	},
+	.probe		= ltc4151_probe,
+	.id_table	= ltc4151_id,
+};
+
+module_i2c_driver(ltc4151_driver);
+
+MODULE_AUTHOR("Per Dalen <per.dalen@appeartv.com>");
+MODULE_DESCRIPTION("LTC4151 driver");
+MODULE_LICENSE("GPL");