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, 339 insertions, 0 deletions

diff --git a/drivers/regulator/max8952.c b/drivers/regulator/max8952.c
new file mode 100644
index 000000000..f8b91a570
--- /dev/null
+++ b/drivers/regulator/max8952.c
@@ -0,0 +1,339 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * max8952.c - Voltage and current regulation for the Maxim 8952
+ *
+ * Copyright (C) 2010 Samsung Electronics
+ * MyungJoo Ham <myungjoo.ham@samsung.com>
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/i2c.h>
+#include <linux/err.h>
+#include <linux/platform_device.h>
+#include <linux/regulator/driver.h>
+#include <linux/regulator/max8952.h>
+#include <linux/gpio/consumer.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/regulator/of_regulator.h>
+#include <linux/slab.h>
+
+/* Registers */
+enum {
+	MAX8952_REG_MODE0,
+	MAX8952_REG_MODE1,
+	MAX8952_REG_MODE2,
+	MAX8952_REG_MODE3,
+	MAX8952_REG_CONTROL,
+	MAX8952_REG_SYNC,
+	MAX8952_REG_RAMP,
+	MAX8952_REG_CHIP_ID1,
+	MAX8952_REG_CHIP_ID2,
+};
+
+struct max8952_data {
+	struct i2c_client	*client;
+	struct max8952_platform_data *pdata;
+	struct gpio_desc *vid0_gpiod;
+	struct gpio_desc *vid1_gpiod;
+	bool vid0;
+	bool vid1;
+};
+
+static int max8952_read_reg(struct max8952_data *max8952, u8 reg)
+{
+	int ret = i2c_smbus_read_byte_data(max8952->client, reg);
+
+	if (ret > 0)
+		ret &= 0xff;
+
+	return ret;
+}
+
+static int max8952_write_reg(struct max8952_data *max8952,
+		u8 reg, u8 value)
+{
+	return i2c_smbus_write_byte_data(max8952->client, reg, value);
+}
+
+static int max8952_list_voltage(struct regulator_dev *rdev,
+		unsigned int selector)
+{
+	struct max8952_data *max8952 = rdev_get_drvdata(rdev);
+
+	if (rdev_get_id(rdev) != 0)
+		return -EINVAL;
+
+	return (max8952->pdata->dvs_mode[selector] * 10 + 770) * 1000;
+}
+
+static int max8952_get_voltage_sel(struct regulator_dev *rdev)
+{
+	struct max8952_data *max8952 = rdev_get_drvdata(rdev);
+	u8 vid = 0;
+
+	if (max8952->vid0)
+		vid += 1;
+	if (max8952->vid1)
+		vid += 2;
+
+	return vid;
+}
+
+static int max8952_set_voltage_sel(struct regulator_dev *rdev,
+				   unsigned selector)
+{
+	struct max8952_data *max8952 = rdev_get_drvdata(rdev);
+
+	if (!max8952->vid0_gpiod || !max8952->vid1_gpiod) {
+		/* DVS not supported */
+		return -EPERM;
+	}
+
+	max8952->vid0 = selector & 0x1;
+	max8952->vid1 = (selector >> 1) & 0x1;
+	gpiod_set_value(max8952->vid0_gpiod, max8952->vid0);
+	gpiod_set_value(max8952->vid1_gpiod, max8952->vid1);
+
+	return 0;
+}
+
+static const struct regulator_ops max8952_ops = {
+	.list_voltage		= max8952_list_voltage,
+	.get_voltage_sel	= max8952_get_voltage_sel,
+	.set_voltage_sel	= max8952_set_voltage_sel,
+};
+
+static const struct regulator_desc regulator = {
+	.name		= "MAX8952_VOUT",
+	.id		= 0,
+	.n_voltages	= MAX8952_NUM_DVS_MODE,
+	.ops		= &max8952_ops,
+	.type		= REGULATOR_VOLTAGE,
+	.owner		= THIS_MODULE,
+};
+
+#ifdef CONFIG_OF
+static const struct of_device_id max8952_dt_match[] = {
+	{ .compatible = "maxim,max8952" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, max8952_dt_match);
+
+static struct max8952_platform_data *max8952_parse_dt(struct device *dev)
+{
+	struct max8952_platform_data *pd;
+	struct device_node *np = dev->of_node;
+	int ret;
+	int i;
+
+	pd = devm_kzalloc(dev, sizeof(*pd), GFP_KERNEL);
+	if (!pd)
+		return NULL;
+
+	if (of_property_read_u32(np, "max8952,default-mode", &pd->default_mode))
+		dev_warn(dev, "Default mode not specified, assuming 0\n");
+
+	ret = of_property_read_u32_array(np, "max8952,dvs-mode-microvolt",
+					pd->dvs_mode, ARRAY_SIZE(pd->dvs_mode));
+	if (ret) {
+		dev_err(dev, "max8952,dvs-mode-microvolt property not specified");
+		return NULL;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(pd->dvs_mode); ++i) {
+		if (pd->dvs_mode[i] < 770000 || pd->dvs_mode[i] > 1400000) {
+			dev_err(dev, "DVS voltage %d out of range\n", i);
+			return NULL;
+		}
+		pd->dvs_mode[i] = (pd->dvs_mode[i] - 770000) / 10000;
+	}
+
+	if (of_property_read_u32(np, "max8952,sync-freq", &pd->sync_freq))
+		dev_warn(dev, "max8952,sync-freq property not specified, defaulting to 26MHz\n");
+
+	if (of_property_read_u32(np, "max8952,ramp-speed", &pd->ramp_speed))
+		dev_warn(dev, "max8952,ramp-speed property not specified, defaulting to 32mV/us\n");
+
+	pd->reg_data = of_get_regulator_init_data(dev, np, &regulator);
+	if (!pd->reg_data) {
+		dev_err(dev, "Failed to parse regulator init data\n");
+		return NULL;
+	}
+
+	return pd;
+}
+#else
+static struct max8952_platform_data *max8952_parse_dt(struct device *dev)
+{
+	return NULL;
+}
+#endif
+
+static int max8952_pmic_probe(struct i2c_client *client)
+{
+	struct i2c_adapter *adapter = client->adapter;
+	struct max8952_platform_data *pdata = dev_get_platdata(&client->dev);
+	struct regulator_config config = { };
+	struct max8952_data *max8952;
+	struct regulator_dev *rdev;
+	struct gpio_desc *gpiod;
+	enum gpiod_flags gflags;
+
+	int ret = 0;
+
+	if (client->dev.of_node)
+		pdata = max8952_parse_dt(&client->dev);
+
+	if (!pdata) {
+		dev_err(&client->dev, "Require the platform data\n");
+		return -EINVAL;
+	}
+
+	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE))
+		return -EIO;
+
+	max8952 = devm_kzalloc(&client->dev, sizeof(struct max8952_data),
+			       GFP_KERNEL);
+	if (!max8952)
+		return -ENOMEM;
+
+	max8952->client = client;
+	max8952->pdata = pdata;
+
+	config.dev = &client->dev;
+	config.init_data = pdata->reg_data;
+	config.driver_data = max8952;
+	config.of_node = client->dev.of_node;
+
+	if (pdata->reg_data->constraints.boot_on)
+		gflags = GPIOD_OUT_HIGH;
+	else
+		gflags = GPIOD_OUT_LOW;
+	gflags |= GPIOD_FLAGS_BIT_NONEXCLUSIVE;
+	/*
+	 * Do not use devm* here: the regulator core takes over the
+	 * lifecycle management of the GPIO descriptor.
+	 */
+	gpiod = gpiod_get_optional(&client->dev,
+				   "max8952,en",
+				   gflags);
+	if (IS_ERR(gpiod))
+		return PTR_ERR(gpiod);
+	if (gpiod)
+		config.ena_gpiod = gpiod;
+
+	rdev = devm_regulator_register(&client->dev, &regulator, &config);
+	if (IS_ERR(rdev)) {
+		ret = PTR_ERR(rdev);
+		dev_err(&client->dev, "regulator init failed (%d)\n", ret);
+		return ret;
+	}
+
+	max8952->vid0 = pdata->default_mode & 0x1;
+	max8952->vid1 = (pdata->default_mode >> 1) & 0x1;
+
+	/* Fetch vid0 and vid1 GPIOs if available */
+	gflags = max8952->vid0 ? GPIOD_OUT_HIGH : GPIOD_OUT_LOW;
+	max8952->vid0_gpiod = devm_gpiod_get_index_optional(&client->dev,
+							    "max8952,vid",
+							    0, gflags);
+	if (IS_ERR(max8952->vid0_gpiod))
+		return PTR_ERR(max8952->vid0_gpiod);
+	gflags = max8952->vid1 ? GPIOD_OUT_HIGH : GPIOD_OUT_LOW;
+	max8952->vid1_gpiod = devm_gpiod_get_index_optional(&client->dev,
+							    "max8952,vid",
+							    1, gflags);
+	if (IS_ERR(max8952->vid1_gpiod))
+		return PTR_ERR(max8952->vid1_gpiod);
+
+	/* If either VID GPIO is missing just disable this */
+	if (!max8952->vid0_gpiod || !max8952->vid1_gpiod) {
+		dev_warn(&client->dev, "VID0/1 gpio invalid: "
+			 "DVS not available.\n");
+		max8952->vid0 = 0;
+		max8952->vid1 = 0;
+		/* Make sure if we have any descriptors they get set to low */
+		if (max8952->vid0_gpiod)
+			gpiod_set_value(max8952->vid0_gpiod, 0);
+		if (max8952->vid1_gpiod)
+			gpiod_set_value(max8952->vid1_gpiod, 0);
+
+		/* Disable Pulldown of EN only */
+		max8952_write_reg(max8952, MAX8952_REG_CONTROL, 0x60);
+
+		dev_err(&client->dev, "DVS modes disabled because VID0 and VID1"
+				" do not have proper controls.\n");
+	} else {
+		/*
+		 * Disable Pulldown on EN, VID0, VID1 to reduce
+		 * leakage current of MAX8952 assuming that MAX8952
+		 * is turned on (EN==1). Note that without having VID0/1
+		 * properly connected, turning pulldown off can be
+		 * problematic. Thus, turn this off only when they are
+		 * controllable by GPIO.
+		 */
+		max8952_write_reg(max8952, MAX8952_REG_CONTROL, 0x0);
+	}
+
+	max8952_write_reg(max8952, MAX8952_REG_MODE0,
+			(max8952_read_reg(max8952,
+					  MAX8952_REG_MODE0) & 0xC0) |
+			(pdata->dvs_mode[0] & 0x3F));
+	max8952_write_reg(max8952, MAX8952_REG_MODE1,
+			(max8952_read_reg(max8952,
+					  MAX8952_REG_MODE1) & 0xC0) |
+			(pdata->dvs_mode[1] & 0x3F));
+	max8952_write_reg(max8952, MAX8952_REG_MODE2,
+			(max8952_read_reg(max8952,
+					  MAX8952_REG_MODE2) & 0xC0) |
+			(pdata->dvs_mode[2] & 0x3F));
+	max8952_write_reg(max8952, MAX8952_REG_MODE3,
+			(max8952_read_reg(max8952,
+					  MAX8952_REG_MODE3) & 0xC0) |
+			(pdata->dvs_mode[3] & 0x3F));
+
+	max8952_write_reg(max8952, MAX8952_REG_SYNC,
+			(max8952_read_reg(max8952, MAX8952_REG_SYNC) & 0x3F) |
+			((pdata->sync_freq & 0x3) << 6));
+	max8952_write_reg(max8952, MAX8952_REG_RAMP,
+			(max8952_read_reg(max8952, MAX8952_REG_RAMP) & 0x1F) |
+			((pdata->ramp_speed & 0x7) << 5));
+
+	i2c_set_clientdata(client, max8952);
+
+	return 0;
+}
+
+static const struct i2c_device_id max8952_ids[] = {
+	{ .name = "max8952" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, max8952_ids);
+
+static struct i2c_driver max8952_pmic_driver = {
+	.probe		= max8952_pmic_probe,
+	.driver		= {
+		.name	= "max8952",
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+		.of_match_table = of_match_ptr(max8952_dt_match),
+	},
+	.id_table	= max8952_ids,
+};
+
+static int __init max8952_pmic_init(void)
+{
+	return i2c_add_driver(&max8952_pmic_driver);
+}
+subsys_initcall(max8952_pmic_init);
+
+static void __exit max8952_pmic_exit(void)
+{
+	i2c_del_driver(&max8952_pmic_driver);
+}
+module_exit(max8952_pmic_exit);
+
+MODULE_DESCRIPTION("MAXIM 8952 voltage regulator driver");
+MODULE_AUTHOR("MyungJoo Ham <myungjoo.ham@samsung.com>");
+MODULE_LICENSE("GPL");