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, 357 insertions, 0 deletions

diff --git a/drivers/power/reset/reboot-mode.c b/drivers/power/reset/reboot-mode.c
new file mode 100644
index 000000000..3611bed34
--- /dev/null
+++ b/drivers/power/reset/reboot-mode.c
@@ -0,0 +1,357 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2016, Fuzhou Rockchip Electronics Co., Ltd
+ */
+
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/property.h>
+#include <linux/reboot.h>
+#include <linux/reboot-mode.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+
+#define PREFIX "mode-"
+
+struct mode_info {
+	const char *mode;
+	u32 magic;
+	struct list_head list;
+};
+
+struct reboot_mode_sysfs_data {
+	struct device *reboot_mode_device;
+	struct list_head head;
+};
+
+static inline void reboot_mode_release_list(struct reboot_mode_sysfs_data *priv)
+{
+	struct mode_info *info;
+	struct mode_info *next;
+
+	list_for_each_entry_safe(info, next, &priv->head, list) {
+		list_del(&info->list);
+		kfree_const(info->mode);
+		kfree(info);
+	}
+}
+
+static ssize_t reboot_modes_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct reboot_mode_sysfs_data *priv;
+	struct mode_info *sysfs_info;
+	ssize_t size = 0;
+
+	priv = dev_get_drvdata(dev);
+	if (!priv)
+		return -ENODATA;
+
+	list_for_each_entry(sysfs_info, &priv->head, list)
+		size += sysfs_emit_at(buf, size, "%s ", sysfs_info->mode);
+
+	if (!size)
+		return -ENODATA;
+
+	return size + sysfs_emit_at(buf, size - 1, "\n");
+}
+static DEVICE_ATTR_RO(reboot_modes);
+
+static struct attribute *reboot_mode_attrs[] = {
+	&dev_attr_reboot_modes.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(reboot_mode);
+
+static const struct class reboot_mode_class = {
+	.name = "reboot-mode",
+	.dev_groups = reboot_mode_groups,
+};
+
+static unsigned int get_reboot_mode_magic(struct reboot_mode_driver *reboot,
+					  const char *cmd)
+{
+	const char *normal = "normal";
+	struct mode_info *info;
+	char cmd_[110];
+
+	if (!cmd)
+		cmd = normal;
+
+	list_for_each_entry(info, &reboot->head, list)
+		if (!strcmp(info->mode, cmd))
+			return info->magic;
+
+	/* try to match again, replacing characters impossible in DT */
+	if (strscpy(cmd_, cmd, sizeof(cmd_)) == -E2BIG)
+		return 0;
+
+	strreplace(cmd_, ' ', '-');
+	strreplace(cmd_, ',', '-');
+	strreplace(cmd_, '/', '-');
+
+	list_for_each_entry(info, &reboot->head, list)
+		if (!strcmp(info->mode, cmd_))
+			return info->magic;
+
+	return 0;
+}
+
+static int reboot_mode_notify(struct notifier_block *this,
+			      unsigned long mode, void *cmd)
+{
+	struct reboot_mode_driver *reboot;
+	unsigned int magic;
+
+	reboot = container_of(this, struct reboot_mode_driver, reboot_notifier);
+	magic = get_reboot_mode_magic(reboot, cmd);
+	if (magic)
+		reboot->write(reboot, magic);
+
+	return NOTIFY_DONE;
+}
+
+static int reboot_mode_create_device(struct reboot_mode_driver *reboot)
+{
+	struct reboot_mode_sysfs_data *priv;
+	struct mode_info *sysfs_info;
+	struct mode_info *info;
+	int ret;
+
+	priv = kzalloc_obj(*priv);
+	if (!priv)
+		return -ENOMEM;
+
+	INIT_LIST_HEAD(&priv->head);
+
+	list_for_each_entry(info, &reboot->head, list) {
+		sysfs_info = kzalloc_obj(*sysfs_info);
+		if (!sysfs_info) {
+			ret = -ENOMEM;
+			goto error;
+		}
+
+		sysfs_info->mode = kstrdup_const(info->mode, GFP_KERNEL);
+		if (!sysfs_info->mode) {
+			kfree(sysfs_info);
+			ret = -ENOMEM;
+			goto error;
+		}
+
+		list_add_tail(&sysfs_info->list, &priv->head);
+	}
+
+	priv->reboot_mode_device = device_create(&reboot_mode_class, NULL, 0,
+						 (void *)priv, "%s",
+						 reboot->dev->driver->name);
+	if (IS_ERR(priv->reboot_mode_device)) {
+		ret = PTR_ERR(priv->reboot_mode_device);
+		goto error;
+	}
+
+	return 0;
+
+error:
+	reboot_mode_release_list(priv);
+	kfree(priv);
+	return ret;
+}
+
+/**
+ * reboot_mode_register - register a reboot mode driver
+ * @reboot: reboot mode driver
+ *
+ * Returns: 0 on success or a negative error code on failure.
+ */
+int reboot_mode_register(struct reboot_mode_driver *reboot)
+{
+	struct mode_info *info = NULL;
+	struct property *prop;
+	struct device_node *np = reboot->dev->of_node;
+	size_t len = strlen(PREFIX);
+	u32 magic;
+	int ret;
+
+	INIT_LIST_HEAD(&reboot->head);
+
+	for_each_property_of_node(np, prop) {
+		if (strncmp(prop->name, PREFIX, len))
+			continue;
+
+		if (device_property_read_u32(reboot->dev, prop->name, &magic)) {
+			dev_dbg(reboot->dev, "reboot mode %s without magic number\n",
+				prop->name);
+			continue;
+		}
+
+		info = kzalloc_obj(*info);
+		if (!info) {
+			ret = -ENOMEM;
+			goto error;
+		}
+
+		info->magic = magic;
+		info->mode = kstrdup_const(prop->name + len, GFP_KERNEL);
+		if (!info->mode) {
+			ret = -ENOMEM;
+			goto error;
+		} else if (info->mode[0] == '\0') {
+			kfree_const(info->mode);
+			ret = -EINVAL;
+			dev_err(reboot->dev, "invalid mode name(%s): too short!\n",
+				prop->name);
+			goto error;
+		}
+
+		list_add_tail(&info->list, &reboot->head);
+		info = NULL;
+	}
+
+	reboot->reboot_notifier.notifier_call = reboot_mode_notify;
+	register_reboot_notifier(&reboot->reboot_notifier);
+
+	ret = reboot_mode_create_device(reboot);
+	if (ret)
+		goto error;
+
+	return 0;
+
+error:
+	kfree(info);
+	reboot_mode_unregister(reboot);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(reboot_mode_register);
+
+static int reboot_mode_match_by_name(struct device *dev, const void *data)
+{
+	const char *name = data;
+
+	if (!dev || !data)
+		return 0;
+
+	return dev_name(dev) && strcmp(dev_name(dev), name) == 0;
+}
+
+static inline void reboot_mode_unregister_device(struct reboot_mode_driver *reboot)
+{
+	struct reboot_mode_sysfs_data *priv;
+	struct device *reboot_mode_device;
+
+	reboot_mode_device = class_find_device(&reboot_mode_class, NULL, reboot->dev->driver->name,
+					       reboot_mode_match_by_name);
+
+	if (!reboot_mode_device)
+		return;
+
+	priv = dev_get_drvdata(reboot_mode_device);
+	device_unregister(reboot_mode_device);
+
+	if (!priv)
+		return;
+
+	reboot_mode_release_list(priv);
+	kfree(priv);
+}
+
+/**
+ * reboot_mode_unregister - unregister a reboot mode driver
+ * @reboot: reboot mode driver
+ */
+int reboot_mode_unregister(struct reboot_mode_driver *reboot)
+{
+	struct mode_info *info;
+	struct mode_info *next;
+
+	unregister_reboot_notifier(&reboot->reboot_notifier);
+	reboot_mode_unregister_device(reboot);
+
+	list_for_each_entry_safe(info, next, &reboot->head, list) {
+		list_del(&info->list);
+		kfree_const(info->mode);
+		kfree(info);
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(reboot_mode_unregister);
+
+static void devm_reboot_mode_release(struct device *dev, void *res)
+{
+	reboot_mode_unregister(*(struct reboot_mode_driver **)res);
+}
+
+/**
+ * devm_reboot_mode_register() - resource managed reboot_mode_register()
+ * @dev: device to associate this resource with
+ * @reboot: reboot mode driver
+ *
+ * Returns: 0 on success or a negative error code on failure.
+ */
+int devm_reboot_mode_register(struct device *dev,
+			      struct reboot_mode_driver *reboot)
+{
+	struct reboot_mode_driver **dr;
+	int rc;
+
+	dr = devres_alloc(devm_reboot_mode_release, sizeof(*dr), GFP_KERNEL);
+	if (!dr)
+		return -ENOMEM;
+
+	rc = reboot_mode_register(reboot);
+	if (rc) {
+		devres_free(dr);
+		return rc;
+	}
+
+	*dr = reboot;
+	devres_add(dev, dr);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(devm_reboot_mode_register);
+
+static int devm_reboot_mode_match(struct device *dev, void *res, void *data)
+{
+	struct reboot_mode_driver **p = res;
+
+	if (WARN_ON(!p || !*p))
+		return 0;
+
+	return *p == data;
+}
+
+/**
+ * devm_reboot_mode_unregister() - resource managed reboot_mode_unregister()
+ * @dev: device to associate this resource with
+ * @reboot: reboot mode driver
+ */
+void devm_reboot_mode_unregister(struct device *dev,
+				 struct reboot_mode_driver *reboot)
+{
+	WARN_ON(devres_release(dev,
+			       devm_reboot_mode_release,
+			       devm_reboot_mode_match, reboot));
+}
+EXPORT_SYMBOL_GPL(devm_reboot_mode_unregister);
+
+static int __init reboot_mode_init(void)
+{
+	return class_register(&reboot_mode_class);
+}
+
+static void __exit reboot_mode_exit(void)
+{
+	class_unregister(&reboot_mode_class);
+}
+
+subsys_initcall(reboot_mode_init);
+module_exit(reboot_mode_exit);
+
+MODULE_AUTHOR("Andy Yan <andy.yan@rock-chips.com>");
+MODULE_DESCRIPTION("System reboot mode core library");
+MODULE_LICENSE("GPL v2");