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, 213 insertions, 0 deletions

diff --git a/drivers/mfd/as3711.c b/drivers/mfd/as3711.c
new file mode 100644
index 000000000..974197703
--- /dev/null
+++ b/drivers/mfd/as3711.c
@@ -0,0 +1,213 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * AS3711 PMIC MFC driver
+ *
+ * Copyright (C) 2012 Renesas Electronics Corporation
+ * Author: Guennadi Liakhovetski, <g.liakhovetski@gmx.de>
+ */
+
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/mfd/as3711.h>
+#include <linux/mfd/core.h>
+#include <linux/of.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+enum {
+	AS3711_REGULATOR,
+	AS3711_BACKLIGHT,
+};
+
+/*
+ * Ok to have it static: it is only used during probing and multiple I2C devices
+ * cannot be probed simultaneously. Just make sure to avoid stale data.
+ */
+static struct mfd_cell as3711_subdevs[] = {
+	[AS3711_REGULATOR] = {.name = "as3711-regulator",},
+	[AS3711_BACKLIGHT] = {.name = "as3711-backlight",},
+};
+
+static bool as3711_volatile_reg(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case AS3711_GPIO_SIGNAL_IN:
+	case AS3711_INTERRUPT_STATUS_1:
+	case AS3711_INTERRUPT_STATUS_2:
+	case AS3711_INTERRUPT_STATUS_3:
+	case AS3711_CHARGER_STATUS_1:
+	case AS3711_CHARGER_STATUS_2:
+	case AS3711_REG_STATUS:
+		return true;
+	}
+	return false;
+}
+
+static bool as3711_precious_reg(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case AS3711_INTERRUPT_STATUS_1:
+	case AS3711_INTERRUPT_STATUS_2:
+	case AS3711_INTERRUPT_STATUS_3:
+		return true;
+	}
+	return false;
+}
+
+static bool as3711_readable_reg(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case AS3711_SD_1_VOLTAGE:
+	case AS3711_SD_2_VOLTAGE:
+	case AS3711_SD_3_VOLTAGE:
+	case AS3711_SD_4_VOLTAGE:
+	case AS3711_LDO_1_VOLTAGE:
+	case AS3711_LDO_2_VOLTAGE:
+	case AS3711_LDO_3_VOLTAGE:
+	case AS3711_LDO_4_VOLTAGE:
+	case AS3711_LDO_5_VOLTAGE:
+	case AS3711_LDO_6_VOLTAGE:
+	case AS3711_LDO_7_VOLTAGE:
+	case AS3711_LDO_8_VOLTAGE:
+	case AS3711_SD_CONTROL:
+	case AS3711_GPIO_SIGNAL_OUT:
+	case AS3711_GPIO_SIGNAL_IN:
+	case AS3711_SD_CONTROL_1:
+	case AS3711_SD_CONTROL_2:
+	case AS3711_CURR_CONTROL:
+	case AS3711_CURR1_VALUE:
+	case AS3711_CURR2_VALUE:
+	case AS3711_CURR3_VALUE:
+	case AS3711_STEPUP_CONTROL_1:
+	case AS3711_STEPUP_CONTROL_2:
+	case AS3711_STEPUP_CONTROL_4:
+	case AS3711_STEPUP_CONTROL_5:
+	case AS3711_REG_STATUS:
+	case AS3711_INTERRUPT_STATUS_1:
+	case AS3711_INTERRUPT_STATUS_2:
+	case AS3711_INTERRUPT_STATUS_3:
+	case AS3711_CHARGER_STATUS_1:
+	case AS3711_CHARGER_STATUS_2:
+	case AS3711_ASIC_ID_1:
+	case AS3711_ASIC_ID_2:
+		return true;
+	}
+	return false;
+}
+
+static const struct regmap_config as3711_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.volatile_reg = as3711_volatile_reg,
+	.readable_reg = as3711_readable_reg,
+	.precious_reg = as3711_precious_reg,
+	.max_register = AS3711_MAX_REG,
+	.num_reg_defaults_raw = AS3711_NUM_REGS,
+	.cache_type = REGCACHE_MAPLE,
+};
+
+#ifdef CONFIG_OF
+static const struct of_device_id as3711_of_match[] = {
+	{.compatible = "ams,as3711",},
+	{}
+};
+#endif
+
+static int as3711_i2c_probe(struct i2c_client *client)
+{
+	struct as3711 *as3711;
+	struct as3711_platform_data *pdata;
+	unsigned int id1, id2;
+	int ret;
+
+	if (!client->dev.of_node) {
+		pdata = dev_get_platdata(&client->dev);
+		if (!pdata)
+			dev_dbg(&client->dev, "Platform data not found\n");
+	} else {
+		pdata = devm_kzalloc(&client->dev,
+				     sizeof(*pdata), GFP_KERNEL);
+		if (!pdata)
+			return -ENOMEM;
+	}
+
+	as3711 = devm_kzalloc(&client->dev, sizeof(struct as3711), GFP_KERNEL);
+	if (!as3711)
+		return -ENOMEM;
+
+	as3711->dev = &client->dev;
+	i2c_set_clientdata(client, as3711);
+
+	if (client->irq)
+		dev_notice(&client->dev, "IRQ not supported yet\n");
+
+	as3711->regmap = devm_regmap_init_i2c(client, &as3711_regmap_config);
+	if (IS_ERR(as3711->regmap)) {
+		ret = PTR_ERR(as3711->regmap);
+		dev_err(&client->dev,
+			"regmap initialization failed: %d\n", ret);
+		return ret;
+	}
+
+	ret = regmap_read(as3711->regmap, AS3711_ASIC_ID_1, &id1);
+	if (!ret)
+		ret = regmap_read(as3711->regmap, AS3711_ASIC_ID_2, &id2);
+	if (ret < 0) {
+		dev_err(&client->dev, "regmap_read() failed: %d\n", ret);
+		return ret;
+	}
+	if (id1 != 0x8b)
+		return -ENODEV;
+	dev_info(as3711->dev, "AS3711 detected: %x:%x\n", id1, id2);
+
+	/*
+	 * We can reuse as3711_subdevs[],
+	 * it will be copied in mfd_add_devices()
+	 */
+	if (pdata) {
+		as3711_subdevs[AS3711_REGULATOR].platform_data =
+			&pdata->regulator;
+		as3711_subdevs[AS3711_REGULATOR].pdata_size =
+			sizeof(pdata->regulator);
+		as3711_subdevs[AS3711_BACKLIGHT].platform_data =
+			&pdata->backlight;
+		as3711_subdevs[AS3711_BACKLIGHT].pdata_size =
+			sizeof(pdata->backlight);
+	} else {
+		as3711_subdevs[AS3711_REGULATOR].platform_data = NULL;
+		as3711_subdevs[AS3711_REGULATOR].pdata_size = 0;
+		as3711_subdevs[AS3711_BACKLIGHT].platform_data = NULL;
+		as3711_subdevs[AS3711_BACKLIGHT].pdata_size = 0;
+	}
+
+	ret = devm_mfd_add_devices(as3711->dev, -1, as3711_subdevs,
+				   ARRAY_SIZE(as3711_subdevs), NULL, 0, NULL);
+	if (ret < 0)
+		dev_err(&client->dev, "add mfd devices failed: %d\n", ret);
+
+	return ret;
+}
+
+static const struct i2c_device_id as3711_i2c_id[] = {
+	{.name = "as3711", .driver_data = 0},
+	{}
+};
+
+static struct i2c_driver as3711_i2c_driver = {
+	.driver = {
+		   .name = "as3711",
+		   .of_match_table = of_match_ptr(as3711_of_match),
+	},
+	.probe = as3711_i2c_probe,
+	.id_table = as3711_i2c_id,
+};
+
+static int __init as3711_i2c_init(void)
+{
+	return i2c_add_driver(&as3711_i2c_driver);
+}
+/* Initialise early */
+subsys_initcall(as3711_i2c_init);