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, 143 insertions, 0 deletions

diff --git a/drivers/misc/hmc6352.c b/drivers/misc/hmc6352.c
new file mode 100644
index 000000000..275dc054c
--- /dev/null
+++ b/drivers/misc/hmc6352.c
@@ -0,0 +1,143 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * hmc6352.c - Honeywell Compass Driver
+ *
+ * Copyright (C) 2009 Intel Corp
+ *
+ *  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ *
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <linux/err.h>
+#include <linux/delay.h>
+#include <linux/sysfs.h>
+#include <linux/nospec.h>
+
+static DEFINE_MUTEX(compass_mutex);
+
+static int compass_command(struct i2c_client *c, u8 cmd)
+{
+	int ret = i2c_master_send(c, &cmd, 1);
+	if (ret < 0)
+		dev_warn(&c->dev, "command '%c' failed.\n", cmd);
+	return ret;
+}
+
+static int compass_store(struct device *dev, const char *buf, size_t count,
+			const char *map)
+{
+	struct i2c_client *c = to_i2c_client(dev);
+	int ret;
+	unsigned long val;
+
+	ret = kstrtoul(buf, 10, &val);
+	if (ret)
+		return ret;
+	if (val >= strlen(map))
+		return -EINVAL;
+	val = array_index_nospec(val, strlen(map));
+	mutex_lock(&compass_mutex);
+	ret = compass_command(c, map[val]);
+	mutex_unlock(&compass_mutex);
+	if (ret < 0)
+		return ret;
+	return count;
+}
+
+static ssize_t compass_calibration_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t count)
+{
+	return compass_store(dev, buf, count, "EC");
+}
+
+static ssize_t compass_power_mode_store(struct device *dev,
+		struct device_attribute *attr, const  char *buf, size_t count)
+{
+	return compass_store(dev, buf, count, "SW");
+}
+
+static ssize_t compass_heading_data_show(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	unsigned char i2c_data[2];
+	int ret;
+
+	mutex_lock(&compass_mutex);
+	ret = compass_command(client, 'A');
+	if (ret != 1) {
+		mutex_unlock(&compass_mutex);
+		return ret;
+	}
+	msleep(10); /* sending 'A' cmd we need to wait for 7-10 millisecs */
+	ret = i2c_master_recv(client, i2c_data, 2);
+	mutex_unlock(&compass_mutex);
+	if (ret < 0) {
+		dev_warn(dev, "i2c read data cmd failed\n");
+		return ret;
+	}
+	ret = (i2c_data[0] << 8) | i2c_data[1];
+	return sprintf(buf, "%d.%d\n", ret/10, ret%10);
+}
+
+
+static DEVICE_ATTR(heading0_input, S_IRUGO, compass_heading_data_show, NULL);
+static DEVICE_ATTR(calibration, S_IWUSR, NULL, compass_calibration_store);
+static DEVICE_ATTR(power_state, S_IWUSR, NULL, compass_power_mode_store);
+
+static struct attribute *mid_att_compass[] = {
+	&dev_attr_heading0_input.attr,
+	&dev_attr_calibration.attr,
+	&dev_attr_power_state.attr,
+	NULL
+};
+
+static const struct attribute_group m_compass_gr = {
+	.name = "hmc6352",
+	.attrs = mid_att_compass
+};
+
+static int hmc6352_probe(struct i2c_client *client)
+{
+	int res;
+
+	res = sysfs_create_group(&client->dev.kobj, &m_compass_gr);
+	if (res) {
+		dev_err(&client->dev, "device_create_file failed\n");
+		return res;
+	}
+	dev_info(&client->dev, "%s HMC6352 compass chip found\n",
+							client->name);
+	return 0;
+}
+
+static void hmc6352_remove(struct i2c_client *client)
+{
+	sysfs_remove_group(&client->dev.kobj, &m_compass_gr);
+}
+
+static const struct i2c_device_id hmc6352_id[] = {
+	{ .name = "hmc6352" },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(i2c, hmc6352_id);
+
+static struct i2c_driver hmc6352_driver = {
+	.driver = {
+		.name = "hmc6352",
+	},
+	.probe = hmc6352_probe,
+	.remove = hmc6352_remove,
+	.id_table = hmc6352_id,
+};
+
+module_i2c_driver(hmc6352_driver);
+
+MODULE_AUTHOR("Kalhan Trisal <kalhan.trisal@intel.com");
+MODULE_DESCRIPTION("hmc6352 Compass Driver");
+MODULE_LICENSE("GPL v2");