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, 321 insertions, 0 deletions

diff --git a/drivers/hwmon/pcf8591.c b/drivers/hwmon/pcf8591.c
new file mode 100644
index 000000000..c0220ebfd
--- /dev/null
+++ b/drivers/hwmon/pcf8591.c
@@ -0,0 +1,321 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2001-2004 Aurelien Jarno <aurelien@aurel32.net>
+ * Ported to Linux 2.6 by Aurelien Jarno <aurelien@aurel32.net> with
+ * the help of Jean Delvare <jdelvare@suse.de>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <linux/mutex.h>
+#include <linux/err.h>
+#include <linux/hwmon.h>
+#include <linux/kstrtox.h>
+
+/* Insmod parameters */
+
+static int input_mode;
+module_param(input_mode, int, 0);
+MODULE_PARM_DESC(input_mode,
+	"Analog input mode:\n"
+	" 0 = four single ended inputs\n"
+	" 1 = three differential inputs\n"
+	" 2 = single ended and differential mixed\n"
+	" 3 = two differential inputs\n");
+
+/*
+ * The PCF8591 control byte
+ *      7    6    5    4    3    2    1    0
+ *   |  0 |AOEF|   AIP   |  0 |AINC|  AICH   |
+ */
+
+/* Analog Output Enable Flag (analog output active if 1) */
+#define PCF8591_CONTROL_AOEF		0x40
+
+/*
+ * Analog Input Programming
+ * 0x00 = four single ended inputs
+ * 0x10 = three differential inputs
+ * 0x20 = single ended and differential mixed
+ * 0x30 = two differential inputs
+ */
+#define PCF8591_CONTROL_AIP_MASK	0x30
+
+/* Autoincrement Flag (switch on if 1) */
+#define PCF8591_CONTROL_AINC		0x04
+
+/*
+ * Channel selection
+ * 0x00 = channel 0
+ * 0x01 = channel 1
+ * 0x02 = channel 2
+ * 0x03 = channel 3
+ */
+#define PCF8591_CONTROL_AICH_MASK	0x03
+
+/* Initial values */
+#define PCF8591_INIT_CONTROL	((input_mode << 4) | PCF8591_CONTROL_AOEF)
+#define PCF8591_INIT_AOUT	0	/* DAC out = 0 */
+
+/* Conversions */
+#define REG_TO_SIGNED(reg)	(((reg) & 0x80) ? ((reg) - 256) : (reg))
+
+struct pcf8591_data {
+	struct device *hwmon_dev;
+	struct mutex update_lock;
+
+	u8 control;
+	u8 aout;
+};
+
+static void pcf8591_init_client(struct i2c_client *client);
+static int pcf8591_read_channel(struct device *dev, int channel);
+
+/* following are the sysfs callback functions */
+#define show_in_channel(channel)					\
+static ssize_t show_in##channel##_input(struct device *dev,		\
+					struct device_attribute *attr,	\
+					char *buf)			\
+{									\
+	return sprintf(buf, "%d\n", pcf8591_read_channel(dev, channel));\
+}									\
+static DEVICE_ATTR(in##channel##_input, S_IRUGO,			\
+		   show_in##channel##_input, NULL);
+
+show_in_channel(0);
+show_in_channel(1);
+show_in_channel(2);
+show_in_channel(3);
+
+static ssize_t out0_output_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct pcf8591_data *data = i2c_get_clientdata(to_i2c_client(dev));
+	return sprintf(buf, "%d\n", data->aout * 10);
+}
+
+static ssize_t out0_output_store(struct device *dev,
+				 struct device_attribute *attr,
+				 const char *buf, size_t count)
+{
+	unsigned long val;
+	struct i2c_client *client = to_i2c_client(dev);
+	struct pcf8591_data *data = i2c_get_clientdata(client);
+	int err;
+
+	err = kstrtoul(buf, 10, &val);
+	if (err)
+		return err;
+
+	val /= 10;
+	if (val > 255)
+		return -EINVAL;
+
+	data->aout = val;
+	i2c_smbus_write_byte_data(client, data->control, data->aout);
+	return count;
+}
+
+static DEVICE_ATTR_RW(out0_output);
+
+static ssize_t out0_enable_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct pcf8591_data *data = i2c_get_clientdata(to_i2c_client(dev));
+	return sprintf(buf, "%u\n", !(!(data->control & PCF8591_CONTROL_AOEF)));
+}
+
+static ssize_t out0_enable_store(struct device *dev,
+				 struct device_attribute *attr,
+				 const char *buf, size_t count)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct pcf8591_data *data = i2c_get_clientdata(client);
+	unsigned long val;
+	int err;
+
+	err = kstrtoul(buf, 10, &val);
+	if (err)
+		return err;
+
+	mutex_lock(&data->update_lock);
+	if (val)
+		data->control |= PCF8591_CONTROL_AOEF;
+	else
+		data->control &= ~PCF8591_CONTROL_AOEF;
+	i2c_smbus_write_byte(client, data->control);
+	mutex_unlock(&data->update_lock);
+	return count;
+}
+
+static DEVICE_ATTR_RW(out0_enable);
+
+static struct attribute *pcf8591_attributes[] = {
+	&dev_attr_out0_enable.attr,
+	&dev_attr_out0_output.attr,
+	&dev_attr_in0_input.attr,
+	&dev_attr_in1_input.attr,
+	NULL
+};
+
+static const struct attribute_group pcf8591_attr_group = {
+	.attrs = pcf8591_attributes,
+};
+
+static struct attribute *pcf8591_attributes_opt[] = {
+	&dev_attr_in2_input.attr,
+	&dev_attr_in3_input.attr,
+	NULL
+};
+
+static const struct attribute_group pcf8591_attr_group_opt = {
+	.attrs = pcf8591_attributes_opt,
+};
+
+/*
+ * Real code
+ */
+
+static int pcf8591_probe(struct i2c_client *client)
+{
+	struct pcf8591_data *data;
+	int err;
+
+	data = devm_kzalloc(&client->dev, sizeof(struct pcf8591_data),
+			    GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	i2c_set_clientdata(client, data);
+	mutex_init(&data->update_lock);
+
+	/* Initialize the PCF8591 chip */
+	pcf8591_init_client(client);
+
+	/* Register sysfs hooks */
+	err = sysfs_create_group(&client->dev.kobj, &pcf8591_attr_group);
+	if (err)
+		return err;
+
+	/* Register input2 if not in "two differential inputs" mode */
+	if (input_mode != 3) {
+		err = device_create_file(&client->dev, &dev_attr_in2_input);
+		if (err)
+			goto exit_sysfs_remove;
+	}
+
+	/* Register input3 only in "four single ended inputs" mode */
+	if (input_mode == 0) {
+		err = device_create_file(&client->dev, &dev_attr_in3_input);
+		if (err)
+			goto exit_sysfs_remove;
+	}
+
+	data->hwmon_dev = hwmon_device_register(&client->dev);
+	if (IS_ERR(data->hwmon_dev)) {
+		err = PTR_ERR(data->hwmon_dev);
+		goto exit_sysfs_remove;
+	}
+
+	return 0;
+
+exit_sysfs_remove:
+	sysfs_remove_group(&client->dev.kobj, &pcf8591_attr_group_opt);
+	sysfs_remove_group(&client->dev.kobj, &pcf8591_attr_group);
+	return err;
+}
+
+static void pcf8591_remove(struct i2c_client *client)
+{
+	struct pcf8591_data *data = i2c_get_clientdata(client);
+
+	hwmon_device_unregister(data->hwmon_dev);
+	sysfs_remove_group(&client->dev.kobj, &pcf8591_attr_group_opt);
+	sysfs_remove_group(&client->dev.kobj, &pcf8591_attr_group);
+}
+
+/* Called when we have found a new PCF8591. */
+static void pcf8591_init_client(struct i2c_client *client)
+{
+	struct pcf8591_data *data = i2c_get_clientdata(client);
+	data->control = PCF8591_INIT_CONTROL;
+	data->aout = PCF8591_INIT_AOUT;
+
+	i2c_smbus_write_byte_data(client, data->control, data->aout);
+
+	/*
+	 * The first byte transmitted contains the conversion code of the
+	 * previous read cycle. FLUSH IT!
+	 */
+	i2c_smbus_read_byte(client);
+}
+
+static int pcf8591_read_channel(struct device *dev, int channel)
+{
+	u8 value;
+	struct i2c_client *client = to_i2c_client(dev);
+	struct pcf8591_data *data = i2c_get_clientdata(client);
+
+	mutex_lock(&data->update_lock);
+
+	if ((data->control & PCF8591_CONTROL_AICH_MASK) != channel) {
+		data->control = (data->control & ~PCF8591_CONTROL_AICH_MASK)
+			      | channel;
+		i2c_smbus_write_byte(client, data->control);
+
+		/*
+		 * The first byte transmitted contains the conversion code of
+		 * the previous read cycle. FLUSH IT!
+		 */
+		i2c_smbus_read_byte(client);
+	}
+	value = i2c_smbus_read_byte(client);
+
+	mutex_unlock(&data->update_lock);
+
+	if ((channel == 2 && input_mode == 2) ||
+	    (channel != 3 && (input_mode == 1 || input_mode == 3)))
+		return 10 * REG_TO_SIGNED(value);
+	else
+		return 10 * value;
+}
+
+static const struct i2c_device_id pcf8591_id[] = {
+	{ .name = "pcf8591" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, pcf8591_id);
+
+static struct i2c_driver pcf8591_driver = {
+	.driver = {
+		.name	= "pcf8591",
+	},
+	.probe		= pcf8591_probe,
+	.remove		= pcf8591_remove,
+	.id_table	= pcf8591_id,
+};
+
+static int __init pcf8591_init(void)
+{
+	if (input_mode < 0 || input_mode > 3) {
+		pr_warn("invalid input_mode (%d)\n", input_mode);
+		input_mode = 0;
+	}
+	return i2c_add_driver(&pcf8591_driver);
+}
+
+static void __exit pcf8591_exit(void)
+{
+	i2c_del_driver(&pcf8591_driver);
+}
+
+MODULE_AUTHOR("Aurelien Jarno <aurelien@aurel32.net>");
+MODULE_DESCRIPTION("PCF8591 driver");
+MODULE_LICENSE("GPL");
+
+module_init(pcf8591_init);
+module_exit(pcf8591_exit);