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, 250 insertions, 0 deletions

diff --git a/drivers/mfd/stw481x.c b/drivers/mfd/stw481x.c
new file mode 100644
index 000000000..5ed64d53c
--- /dev/null
+++ b/drivers/mfd/stw481x.c
@@ -0,0 +1,250 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Core driver for STw4810/STw4811
+ *
+ * Copyright (C) 2013 ST-Ericsson SA
+ * Written on behalf of Linaro for ST-Ericsson
+ *
+ * Author: Linus Walleij <linus.walleij@linaro.org>
+ */
+
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/stw481x.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+#include <linux/spinlock.h>
+#include <linux/slab.h>
+
+/*
+ * This driver can only access the non-USB portions of STw4811, the register
+ * range 0x00-0x10 dealing with USB is bound to the two special I2C pins used
+ * for USB control.
+ */
+
+/* Registers inside the power control address space */
+#define STW_PC_VCORE_SEL	0x05U
+#define STW_PC_VAUX_SEL		0x06U
+#define STW_PC_VPLL_SEL		0x07U
+
+/**
+ * stw481x_get_pctl_reg() - get a power control register
+ * @stw481x: handle to the stw481x chip
+ * @reg: power control register to fetch
+ *
+ * The power control registers is a set of one-time-programmable registers
+ * in its own register space, accessed by writing addess bits to these
+ * two registers: bits 7,6,5 of PCTL_REG_LO corresponds to the 3 LSBs of
+ * the address and bits 8,9 of PCTL_REG_HI corresponds to the 2 MSBs of
+ * the address, forming an address space of 5 bits, i.e. 32 registers
+ * 0x00 ... 0x1f can be obtained.
+ */
+static int stw481x_get_pctl_reg(struct stw481x *stw481x, u8 reg)
+{
+	u8 msb = (reg >> 3) & 0x03;
+	u8 lsb = (reg << 5) & 0xe0;
+	unsigned int val;
+	u8 vrfy;
+	int ret;
+
+	ret = regmap_write(stw481x->map, STW_PCTL_REG_HI, msb);
+	if (ret)
+		return ret;
+	ret = regmap_write(stw481x->map, STW_PCTL_REG_LO, lsb);
+	if (ret)
+		return ret;
+	ret = regmap_read(stw481x->map, STW_PCTL_REG_HI, &val);
+	if (ret)
+		return ret;
+	vrfy = (val & 0x03) << 3;
+	ret = regmap_read(stw481x->map, STW_PCTL_REG_LO, &val);
+	if (ret)
+		return ret;
+	vrfy |= ((val >> 5) & 0x07);
+	if (vrfy != reg)
+		return -EIO;
+	return (val >> 1) & 0x0f;
+}
+
+static int stw481x_startup(struct stw481x *stw481x)
+{
+	/* Voltages multiplied by 100 */
+	static const u8 vcore_val[] = {
+		100, 105, 110, 115, 120, 122, 124, 126, 128,
+		130, 132, 134, 136, 138, 140, 145
+	};
+	static const u8 vpll_val[] = { 105, 120, 130, 180 };
+	static const u8 vaux_val[] = { 15, 18, 25, 28 };
+	u8 vcore;
+	u8 vcore_slp;
+	u8 vpll;
+	u8 vaux;
+	bool vaux_en;
+	bool it_warn;
+	int ret;
+	unsigned int val;
+
+	ret = regmap_read(stw481x->map, STW_CONF1, &val);
+	if (ret)
+		return ret;
+	vaux_en = !!(val & STW_CONF1_PDN_VAUX);
+	it_warn = !!(val & STW_CONF1_IT_WARN);
+
+	dev_info(&stw481x->client->dev, "voltages %s\n",
+		(val & STW_CONF1_V_MONITORING) ? "OK" : "LOW");
+	dev_info(&stw481x->client->dev, "MMC level shifter %s\n",
+		(val & STW_CONF1_MMC_LS_STATUS) ? "high impedance" : "ON");
+	dev_info(&stw481x->client->dev, "VMMC: %s\n",
+		(val & STW_CONF1_PDN_VMMC) ? "ON" : "disabled");
+
+	dev_info(&stw481x->client->dev, "STw481x power control registers:\n");
+
+	ret = stw481x_get_pctl_reg(stw481x, STW_PC_VCORE_SEL);
+	if (ret < 0)
+		return ret;
+	vcore = ret & 0x0f;
+
+	ret = stw481x_get_pctl_reg(stw481x, STW_PC_VAUX_SEL);
+	if (ret < 0)
+		return ret;
+	vaux = (ret >> 2) & 3;
+	vpll = (ret >> 4) & 1; /* Save bit 4 */
+
+	ret = stw481x_get_pctl_reg(stw481x, STW_PC_VPLL_SEL);
+	if (ret < 0)
+		return ret;
+	vpll |= (ret >> 1) & 2;
+
+	dev_info(&stw481x->client->dev, "VCORE: %u.%uV %s\n",
+		vcore_val[vcore] / 100, vcore_val[vcore] % 100,
+		(ret & 4) ? "ON" : "OFF");
+
+	dev_info(&stw481x->client->dev, "VPLL:  %u.%uV %s\n",
+		vpll_val[vpll] / 100, vpll_val[vpll] % 100,
+		(ret & 0x10) ? "ON" : "OFF");
+
+	dev_info(&stw481x->client->dev, "VAUX:  %u.%uV %s\n",
+		vaux_val[vaux] / 10, vaux_val[vaux] % 10,
+		vaux_en ? "ON" : "OFF");
+
+	ret = regmap_read(stw481x->map, STW_CONF2, &val);
+	if (ret)
+		return ret;
+
+	dev_info(&stw481x->client->dev, "TWARN: %s threshold, %s\n",
+		it_warn ? "below" : "above",
+		(val & STW_CONF2_MASK_TWARN) ?
+		 "enabled" : "mask through VDDOK");
+	dev_info(&stw481x->client->dev, "VMMC: %s\n",
+		(val & STW_CONF2_VMMC_EXT) ? "internal" : "external");
+	dev_info(&stw481x->client->dev, "IT WAKE UP: %s\n",
+		(val & STW_CONF2_MASK_IT_WAKE_UP) ? "enabled" : "masked");
+	dev_info(&stw481x->client->dev, "GPO1: %s\n",
+		(val & STW_CONF2_GPO1) ? "low" : "high impedance");
+	dev_info(&stw481x->client->dev, "GPO2: %s\n",
+		(val & STW_CONF2_GPO2) ? "low" : "high impedance");
+
+	ret = regmap_read(stw481x->map, STW_VCORE_SLEEP, &val);
+	if (ret)
+		return ret;
+	vcore_slp = val & 0x0f;
+	dev_info(&stw481x->client->dev, "VCORE SLEEP: %u.%uV\n",
+		vcore_val[vcore_slp] / 100, vcore_val[vcore_slp] % 100);
+
+	return 0;
+}
+
+/*
+ * MFD cells - we have one cell which is selected operation
+ * mode, and we always have a GPIO cell.
+ */
+static struct mfd_cell stw481x_cells[] = {
+	{
+		.of_compatible = "st,stw481x-vmmc",
+		.name = "stw481x-vmmc-regulator",
+		.id = -1,
+	},
+};
+
+static const struct regmap_config stw481x_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+};
+
+static int stw481x_probe(struct i2c_client *client)
+{
+	struct stw481x			*stw481x;
+	int ret;
+	int i;
+
+	stw481x = devm_kzalloc(&client->dev, sizeof(*stw481x), GFP_KERNEL);
+	if (!stw481x)
+		return -ENOMEM;
+
+	i2c_set_clientdata(client, stw481x);
+	stw481x->client = client;
+	stw481x->map = devm_regmap_init_i2c(client, &stw481x_regmap_config);
+	if (IS_ERR(stw481x->map)) {
+		ret = PTR_ERR(stw481x->map);
+		dev_err(&client->dev, "Failed to allocate register map: %d\n",
+			ret);
+		return ret;
+	}
+
+	ret = stw481x_startup(stw481x);
+	if (ret) {
+		dev_err(&client->dev, "chip initialization failed\n");
+		return ret;
+	}
+
+	/* Set up and register the platform devices. */
+	for (i = 0; i < ARRAY_SIZE(stw481x_cells); i++) {
+		/* One state holder for all drivers, this is simple */
+		stw481x_cells[i].platform_data = stw481x;
+		stw481x_cells[i].pdata_size = sizeof(*stw481x);
+	}
+
+	ret = devm_mfd_add_devices(&client->dev, 0, stw481x_cells,
+				   ARRAY_SIZE(stw481x_cells), NULL, 0, NULL);
+	if (ret)
+		return ret;
+
+	dev_info(&client->dev, "initialized STw481x device\n");
+
+	return ret;
+}
+
+/*
+ * This ID table is completely unused, as this is a pure
+ * device-tree probed driver, but it has to be here due to
+ * the structure of the I2C core.
+ */
+static const struct i2c_device_id stw481x_id[] = {
+	{ "stw481x" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, stw481x_id);
+
+static const struct of_device_id stw481x_match[] = {
+	{ .compatible = "st,stw4810", },
+	{ .compatible = "st,stw4811", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, stw481x_match);
+
+static struct i2c_driver stw481x_driver = {
+	.driver = {
+		.name	= "stw481x",
+		.of_match_table = stw481x_match,
+	},
+	.probe		= stw481x_probe,
+	.id_table	= stw481x_id,
+};
+
+module_i2c_driver(stw481x_driver);
+
+MODULE_AUTHOR("Linus Walleij");
+MODULE_DESCRIPTION("STw481x PMIC driver");
+MODULE_LICENSE("GPL v2");