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, 373 insertions, 0 deletions

diff --git a/drivers/regulator/virtual.c b/drivers/regulator/virtual.c
new file mode 100644
index 000000000..218a0d66a
--- /dev/null
+++ b/drivers/regulator/virtual.c
@@ -0,0 +1,373 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * reg-virtual-consumer.c
+ *
+ * Copyright 2008 Wolfson Microelectronics PLC.
+ *
+ * Author: Mark Brown <broonie@opensource.wolfsonmicro.com>
+ */
+
+#include <linux/err.h>
+#include <linux/mutex.h>
+#include <linux/platform_device.h>
+#include <linux/regulator/consumer.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/of.h>
+
+struct virtual_consumer_data {
+	struct mutex lock;
+	struct regulator *regulator;
+	bool enabled;
+	int min_uV;
+	int max_uV;
+	int min_uA;
+	int max_uA;
+	unsigned int mode;
+};
+
+static void update_voltage_constraints(struct device *dev,
+				       struct virtual_consumer_data *data)
+{
+	int ret;
+
+	if (data->min_uV && data->max_uV
+	    && data->min_uV <= data->max_uV) {
+		dev_dbg(dev, "Requesting %d-%duV\n",
+			data->min_uV, data->max_uV);
+		ret = regulator_set_voltage(data->regulator,
+					data->min_uV, data->max_uV);
+		if (ret != 0) {
+			dev_err(dev,
+				"regulator_set_voltage() failed: %d\n", ret);
+			return;
+		}
+	}
+
+	if (data->min_uV && data->max_uV && !data->enabled) {
+		dev_dbg(dev, "Enabling regulator\n");
+		ret = regulator_enable(data->regulator);
+		if (ret == 0)
+			data->enabled = true;
+		else
+			dev_err(dev, "regulator_enable() failed: %d\n",
+				ret);
+	}
+
+	if (!(data->min_uV && data->max_uV) && data->enabled) {
+		dev_dbg(dev, "Disabling regulator\n");
+		ret = regulator_disable(data->regulator);
+		if (ret == 0)
+			data->enabled = false;
+		else
+			dev_err(dev, "regulator_disable() failed: %d\n",
+				ret);
+	}
+}
+
+static void update_current_limit_constraints(struct device *dev,
+					  struct virtual_consumer_data *data)
+{
+	int ret;
+
+	if (data->max_uA
+	    && data->min_uA <= data->max_uA) {
+		dev_dbg(dev, "Requesting %d-%duA\n",
+			data->min_uA, data->max_uA);
+		ret = regulator_set_current_limit(data->regulator,
+					data->min_uA, data->max_uA);
+		if (ret != 0) {
+			dev_err(dev,
+				"regulator_set_current_limit() failed: %d\n",
+				ret);
+			return;
+		}
+	}
+
+	if (data->max_uA && !data->enabled) {
+		dev_dbg(dev, "Enabling regulator\n");
+		ret = regulator_enable(data->regulator);
+		if (ret == 0)
+			data->enabled = true;
+		else
+			dev_err(dev, "regulator_enable() failed: %d\n",
+				ret);
+	}
+
+	if (!(data->min_uA && data->max_uA) && data->enabled) {
+		dev_dbg(dev, "Disabling regulator\n");
+		ret = regulator_disable(data->regulator);
+		if (ret == 0)
+			data->enabled = false;
+		else
+			dev_err(dev, "regulator_disable() failed: %d\n",
+				ret);
+	}
+}
+
+static ssize_t show_min_uV(struct device *dev,
+			   struct device_attribute *attr, char *buf)
+{
+	struct virtual_consumer_data *data = dev_get_drvdata(dev);
+	return sprintf(buf, "%d\n", data->min_uV);
+}
+
+static ssize_t set_min_uV(struct device *dev, struct device_attribute *attr,
+			  const char *buf, size_t count)
+{
+	struct virtual_consumer_data *data = dev_get_drvdata(dev);
+	long val;
+
+	if (kstrtol(buf, 10, &val) != 0)
+		return count;
+
+	mutex_lock(&data->lock);
+
+	data->min_uV = val;
+	update_voltage_constraints(dev, data);
+
+	mutex_unlock(&data->lock);
+
+	return count;
+}
+
+static ssize_t show_max_uV(struct device *dev,
+			   struct device_attribute *attr, char *buf)
+{
+	struct virtual_consumer_data *data = dev_get_drvdata(dev);
+	return sprintf(buf, "%d\n", data->max_uV);
+}
+
+static ssize_t set_max_uV(struct device *dev, struct device_attribute *attr,
+			  const char *buf, size_t count)
+{
+	struct virtual_consumer_data *data = dev_get_drvdata(dev);
+	long val;
+
+	if (kstrtol(buf, 10, &val) != 0)
+		return count;
+
+	mutex_lock(&data->lock);
+
+	data->max_uV = val;
+	update_voltage_constraints(dev, data);
+
+	mutex_unlock(&data->lock);
+
+	return count;
+}
+
+static ssize_t show_min_uA(struct device *dev,
+			   struct device_attribute *attr, char *buf)
+{
+	struct virtual_consumer_data *data = dev_get_drvdata(dev);
+	return sprintf(buf, "%d\n", data->min_uA);
+}
+
+static ssize_t set_min_uA(struct device *dev, struct device_attribute *attr,
+			  const char *buf, size_t count)
+{
+	struct virtual_consumer_data *data = dev_get_drvdata(dev);
+	long val;
+
+	if (kstrtol(buf, 10, &val) != 0)
+		return count;
+
+	mutex_lock(&data->lock);
+
+	data->min_uA = val;
+	update_current_limit_constraints(dev, data);
+
+	mutex_unlock(&data->lock);
+
+	return count;
+}
+
+static ssize_t show_max_uA(struct device *dev,
+			   struct device_attribute *attr, char *buf)
+{
+	struct virtual_consumer_data *data = dev_get_drvdata(dev);
+	return sprintf(buf, "%d\n", data->max_uA);
+}
+
+static ssize_t set_max_uA(struct device *dev, struct device_attribute *attr,
+			  const char *buf, size_t count)
+{
+	struct virtual_consumer_data *data = dev_get_drvdata(dev);
+	long val;
+
+	if (kstrtol(buf, 10, &val) != 0)
+		return count;
+
+	mutex_lock(&data->lock);
+
+	data->max_uA = val;
+	update_current_limit_constraints(dev, data);
+
+	mutex_unlock(&data->lock);
+
+	return count;
+}
+
+static ssize_t show_mode(struct device *dev,
+			 struct device_attribute *attr, char *buf)
+{
+	struct virtual_consumer_data *data = dev_get_drvdata(dev);
+
+	switch (data->mode) {
+	case REGULATOR_MODE_FAST:
+		return sprintf(buf, "fast\n");
+	case REGULATOR_MODE_NORMAL:
+		return sprintf(buf, "normal\n");
+	case REGULATOR_MODE_IDLE:
+		return sprintf(buf, "idle\n");
+	case REGULATOR_MODE_STANDBY:
+		return sprintf(buf, "standby\n");
+	default:
+		return sprintf(buf, "unknown\n");
+	}
+}
+
+static ssize_t set_mode(struct device *dev, struct device_attribute *attr,
+			const char *buf, size_t count)
+{
+	struct virtual_consumer_data *data = dev_get_drvdata(dev);
+	unsigned int mode;
+	int ret;
+
+	/*
+	 * sysfs_streq() doesn't need the \n's, but we add them so the strings
+	 * will be shared with show_mode(), above.
+	 */
+	if (sysfs_streq(buf, "fast\n"))
+		mode = REGULATOR_MODE_FAST;
+	else if (sysfs_streq(buf, "normal\n"))
+		mode = REGULATOR_MODE_NORMAL;
+	else if (sysfs_streq(buf, "idle\n"))
+		mode = REGULATOR_MODE_IDLE;
+	else if (sysfs_streq(buf, "standby\n"))
+		mode = REGULATOR_MODE_STANDBY;
+	else {
+		dev_err(dev, "Configuring invalid mode\n");
+		return count;
+	}
+
+	mutex_lock(&data->lock);
+	ret = regulator_set_mode(data->regulator, mode);
+	if (ret == 0)
+		data->mode = mode;
+	else
+		dev_err(dev, "Failed to configure mode: %d\n", ret);
+	mutex_unlock(&data->lock);
+
+	return count;
+}
+
+static DEVICE_ATTR(min_microvolts, 0664, show_min_uV, set_min_uV);
+static DEVICE_ATTR(max_microvolts, 0664, show_max_uV, set_max_uV);
+static DEVICE_ATTR(min_microamps, 0664, show_min_uA, set_min_uA);
+static DEVICE_ATTR(max_microamps, 0664, show_max_uA, set_max_uA);
+static DEVICE_ATTR(mode, 0664, show_mode, set_mode);
+
+static struct attribute *regulator_virtual_attributes[] = {
+	&dev_attr_min_microvolts.attr,
+	&dev_attr_max_microvolts.attr,
+	&dev_attr_min_microamps.attr,
+	&dev_attr_max_microamps.attr,
+	&dev_attr_mode.attr,
+	NULL
+};
+
+static const struct attribute_group regulator_virtual_attr_group = {
+	.attrs	= regulator_virtual_attributes,
+};
+
+#ifdef CONFIG_OF
+static const struct of_device_id regulator_virtual_consumer_of_match[] = {
+	{ .compatible = "regulator-virtual-consumer" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, regulator_virtual_consumer_of_match);
+#endif
+
+static int regulator_virtual_probe(struct platform_device *pdev)
+{
+	char *reg_id = dev_get_platdata(&pdev->dev);
+	struct virtual_consumer_data *drvdata;
+	static bool warned;
+	int ret;
+
+	if (!warned) {
+		warned = true;
+		pr_warn("**********************************************************\n");
+		pr_warn("**   NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE   **\n");
+		pr_warn("**                                                      **\n");
+		pr_warn("** regulator-virtual-consumer is only for testing and   **\n");
+		pr_warn("** debugging.  Do not use it in a production kernel.    **\n");
+		pr_warn("**                                                      **\n");
+		pr_warn("**   NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE   **\n");
+		pr_warn("**********************************************************\n");
+	}
+
+	drvdata = devm_kzalloc(&pdev->dev, sizeof(struct virtual_consumer_data),
+			       GFP_KERNEL);
+	if (drvdata == NULL)
+		return -ENOMEM;
+
+	/*
+	 * This virtual consumer does not have any hardware-defined supply
+	 * name, so just allow the regulator to be specified in a property
+	 * named "default-supply" when we're being probed from devicetree.
+	 */
+	if (!reg_id && pdev->dev.of_node)
+		reg_id = "default";
+
+	mutex_init(&drvdata->lock);
+
+	drvdata->regulator = devm_regulator_get(&pdev->dev, reg_id);
+	if (IS_ERR(drvdata->regulator))
+		return dev_err_probe(&pdev->dev, PTR_ERR(drvdata->regulator),
+				     "Failed to obtain supply '%s'\n",
+				     reg_id);
+
+	ret = sysfs_create_group(&pdev->dev.kobj,
+				 &regulator_virtual_attr_group);
+	if (ret != 0) {
+		dev_err(&pdev->dev,
+			"Failed to create attribute group: %d\n", ret);
+		return ret;
+	}
+
+	drvdata->mode = regulator_get_mode(drvdata->regulator);
+
+	platform_set_drvdata(pdev, drvdata);
+
+	return 0;
+}
+
+static void regulator_virtual_remove(struct platform_device *pdev)
+{
+	struct virtual_consumer_data *drvdata = platform_get_drvdata(pdev);
+
+	sysfs_remove_group(&pdev->dev.kobj, &regulator_virtual_attr_group);
+
+	if (drvdata->enabled)
+		regulator_disable(drvdata->regulator);
+}
+
+static struct platform_driver regulator_virtual_consumer_driver = {
+	.probe		= regulator_virtual_probe,
+	.remove		= regulator_virtual_remove,
+	.driver		= {
+		.name		= "reg-virt-consumer",
+		.probe_type	= PROBE_PREFER_ASYNCHRONOUS,
+		.of_match_table = of_match_ptr(regulator_virtual_consumer_of_match),
+	},
+};
+
+module_platform_driver(regulator_virtual_consumer_driver);
+
+MODULE_AUTHOR("Mark Brown <broonie@opensource.wolfsonmicro.com>");
+MODULE_DESCRIPTION("Virtual regulator consumer");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:reg-virt-consumer");