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, 156 insertions, 0 deletions

diff --git a/drivers/hwmon/max31722.c b/drivers/hwmon/max31722.c
new file mode 100644
index 000000000..6c5c86c75
--- /dev/null
+++ b/drivers/hwmon/max31722.c
@@ -0,0 +1,156 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * max31722 - hwmon driver for Maxim Integrated MAX31722/MAX31723 SPI
+ * digital thermometer and thermostats.
+ *
+ * Copyright (c) 2016, Intel Corporation.
+ */
+
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/spi/spi.h>
+#include <linux/sysfs.h>
+
+#define MAX31722_REG_CFG				0x00
+#define MAX31722_REG_TEMP_LSB				0x01
+
+#define MAX31722_MODE_CONTINUOUS			0x00
+#define MAX31722_MODE_STANDBY				0x01
+#define MAX31722_MODE_MASK				0xFE
+#define MAX31722_RESOLUTION_12BIT			0x06
+#define MAX31722_WRITE_MASK				0x80
+
+struct max31722_data {
+	struct device *hwmon_dev;
+	struct spi_device *spi_device;
+	u8 mode;
+};
+
+static int max31722_set_mode(struct max31722_data *data, u8 mode)
+{
+	int ret;
+	struct spi_device *spi = data->spi_device;
+	u8 buf[2] = {
+		MAX31722_REG_CFG | MAX31722_WRITE_MASK,
+		(data->mode & MAX31722_MODE_MASK) | mode
+	};
+
+	ret = spi_write(spi, &buf, sizeof(buf));
+	if (ret < 0) {
+		dev_err(&spi->dev, "failed to set sensor mode.\n");
+		return ret;
+	}
+	data->mode = (data->mode & MAX31722_MODE_MASK) | mode;
+
+	return 0;
+}
+
+static ssize_t max31722_temp_show(struct device *dev,
+				  struct device_attribute *attr, char *buf)
+{
+	ssize_t ret;
+	struct max31722_data *data = dev_get_drvdata(dev);
+
+	ret = spi_w8r16(data->spi_device, MAX31722_REG_TEMP_LSB);
+	if (ret < 0)
+		return ret;
+	/* Keep 12 bits and multiply by the scale of 62.5 millidegrees/bit. */
+	return sysfs_emit(buf, "%d\n", (s16)le16_to_cpu(ret) * 125 / 32);
+}
+
+static SENSOR_DEVICE_ATTR_RO(temp1_input, max31722_temp, 0);
+
+static struct attribute *max31722_attrs[] = {
+	&sensor_dev_attr_temp1_input.dev_attr.attr,
+	NULL,
+};
+
+ATTRIBUTE_GROUPS(max31722);
+
+static int max31722_probe(struct spi_device *spi)
+{
+	int ret;
+	struct max31722_data *data;
+
+	data = devm_kzalloc(&spi->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	spi_set_drvdata(spi, data);
+	data->spi_device = spi;
+	/*
+	 * Set SD bit to 0 so we can have continuous measurements.
+	 * Set resolution to 12 bits for maximum precision.
+	 */
+	data->mode = MAX31722_MODE_CONTINUOUS | MAX31722_RESOLUTION_12BIT;
+	ret = max31722_set_mode(data, MAX31722_MODE_CONTINUOUS);
+	if (ret < 0)
+		return ret;
+
+	data->hwmon_dev = hwmon_device_register_with_groups(&spi->dev,
+							    spi->modalias,
+							    data,
+							    max31722_groups);
+	if (IS_ERR(data->hwmon_dev)) {
+		max31722_set_mode(data, MAX31722_MODE_STANDBY);
+		return PTR_ERR(data->hwmon_dev);
+	}
+
+	return 0;
+}
+
+static void max31722_remove(struct spi_device *spi)
+{
+	struct max31722_data *data = spi_get_drvdata(spi);
+	int ret;
+
+	hwmon_device_unregister(data->hwmon_dev);
+
+	ret = max31722_set_mode(data, MAX31722_MODE_STANDBY);
+	if (ret)
+		/* There is nothing we can do about this ... */
+		dev_warn(&spi->dev, "Failed to put device in stand-by mode\n");
+}
+
+static int max31722_suspend(struct device *dev)
+{
+	struct spi_device *spi_device = to_spi_device(dev);
+	struct max31722_data *data = spi_get_drvdata(spi_device);
+
+	return max31722_set_mode(data, MAX31722_MODE_STANDBY);
+}
+
+static int max31722_resume(struct device *dev)
+{
+	struct spi_device *spi_device = to_spi_device(dev);
+	struct max31722_data *data = spi_get_drvdata(spi_device);
+
+	return max31722_set_mode(data, MAX31722_MODE_CONTINUOUS);
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(max31722_pm_ops, max31722_suspend, max31722_resume);
+
+static const struct spi_device_id max31722_spi_id[] = {
+	{"max31722", 0},
+	{"max31723", 0},
+	{}
+};
+MODULE_DEVICE_TABLE(spi, max31722_spi_id);
+
+static struct spi_driver max31722_driver = {
+	.driver = {
+		.name = "max31722",
+		.pm = pm_sleep_ptr(&max31722_pm_ops),
+	},
+	.probe =            max31722_probe,
+	.remove =           max31722_remove,
+	.id_table =         max31722_spi_id,
+};
+
+module_spi_driver(max31722_driver);
+
+MODULE_AUTHOR("Tiberiu Breana <tiberiu.a.breana@intel.com>");
+MODULE_DESCRIPTION("max31722 sensor driver");
+MODULE_LICENSE("GPL v2");