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, 144 insertions, 0 deletions

diff --git a/drivers/mfd/simple-mfd-i2c.c b/drivers/mfd/simple-mfd-i2c.c
new file mode 100644
index 000000000..ef3ce4bdf
--- /dev/null
+++ b/drivers/mfd/simple-mfd-i2c.c
@@ -0,0 +1,144 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Simple MFD - I2C
+ *
+ * Author(s):
+ * 	Michael Walle <michael@walle.cc>
+ * 	Lee Jones <lee.jones@linaro.org>
+ *
+ * This driver creates a single register map with the intention for it to be
+ * shared by all sub-devices.  Children can use their parent's device structure
+ * (dev.parent) in order to reference it.
+ *
+ * Once the register map has been successfully initialised, any sub-devices
+ * represented by child nodes in Device Tree or via the MFD cells in this file
+ * will be subsequently registered.
+ */
+
+#include <linux/array_size.h>
+#include <linux/dev_printk.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/mfd/core.h>
+#include <linux/module.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+#include <linux/stddef.h>
+
+#include "simple-mfd-i2c.h"
+
+static const struct regmap_config regmap_config_8r_8v = {
+	.reg_bits = 8,
+	.val_bits = 8,
+};
+
+static int simple_mfd_i2c_probe(struct i2c_client *i2c)
+{
+	const struct simple_mfd_data *simple_mfd_data;
+	const struct regmap_config *regmap_config;
+	struct regmap *regmap;
+	int ret;
+
+	simple_mfd_data = device_get_match_data(&i2c->dev);
+
+	/* If no regmap_config is specified, use the default 8reg and 8val bits */
+	if (!simple_mfd_data || !simple_mfd_data->regmap_config)
+		regmap_config = &regmap_config_8r_8v;
+	else
+		regmap_config = simple_mfd_data->regmap_config;
+
+	regmap = devm_regmap_init_i2c(i2c, regmap_config);
+	if (IS_ERR(regmap))
+		return PTR_ERR(regmap);
+
+	/* If no MFD cells are specified, register using the DT child nodes instead */
+	if (!simple_mfd_data || !simple_mfd_data->mfd_cell)
+		return devm_of_platform_populate(&i2c->dev);
+
+	ret = devm_mfd_add_devices(&i2c->dev, PLATFORM_DEVID_AUTO,
+				   simple_mfd_data->mfd_cell,
+				   simple_mfd_data->mfd_cell_size,
+				   NULL, 0, NULL);
+	if (ret)
+		dev_err(&i2c->dev, "Failed to add child devices\n");
+
+	return ret;
+}
+
+static const struct mfd_cell sy7636a_cells[] = {
+	{ .name = "sy7636a-regulator", },
+	{ .name = "sy7636a-temperature", },
+};
+
+static const struct simple_mfd_data silergy_sy7636a = {
+	.mfd_cell = sy7636a_cells,
+	.mfd_cell_size = ARRAY_SIZE(sy7636a_cells),
+};
+
+static const struct mfd_cell max5970_cells[] = {
+	{ .name = "max5970-regulator", },
+	{ .name = "max5970-iio", },
+	{ .name = "max5970-led", },
+};
+
+static const struct simple_mfd_data maxim_max5970 = {
+	.mfd_cell = max5970_cells,
+	.mfd_cell_size = ARRAY_SIZE(max5970_cells),
+};
+
+static const struct mfd_cell max77705_sensor_cells[] = {
+	{ .name = "max77705-battery" },
+	{ .name = "max77705-hwmon", },
+};
+
+static const struct simple_mfd_data maxim_mon_max77705 = {
+	.mfd_cell = max77705_sensor_cells,
+	.mfd_cell_size = ARRAY_SIZE(max77705_sensor_cells),
+};
+
+static const struct regmap_config spacemit_p1_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+};
+
+static const struct mfd_cell spacemit_p1_cells[] = {
+	{ .name = "spacemit-p1-reboot", },
+	{ .name = "spacemit-p1-regulator", },
+	{ .name = "spacemit-p1-rtc", },
+};
+
+static const struct simple_mfd_data spacemit_p1 = {
+	.regmap_config = &spacemit_p1_regmap_config,
+	.mfd_cell = spacemit_p1_cells,
+	.mfd_cell_size = ARRAY_SIZE(spacemit_p1_cells),
+};
+
+static const struct of_device_id simple_mfd_i2c_of_match[] = {
+	{ .compatible = "delta,tn48m-cpld" },
+	{ .compatible = "fsl,ls1028aqds-fpga" },
+	{ .compatible = "fsl,lx2160aqds-fpga" },
+	{ .compatible = "fsl,lx2160ardb-fpga" },
+	{ .compatible = "kontron,sl28cpld" },
+	{ .compatible = "maxim,max5970", .data = &maxim_max5970 },
+	{ .compatible = "maxim,max5978", .data = &maxim_max5970 },
+	{ .compatible = "maxim,max77705-battery", .data = &maxim_mon_max77705 },
+	{ .compatible = "silergy,sy7636a", .data = &silergy_sy7636a },
+	{ .compatible = "spacemit,p1", .data = &spacemit_p1 },
+	{}
+};
+MODULE_DEVICE_TABLE(of, simple_mfd_i2c_of_match);
+
+static struct i2c_driver simple_mfd_i2c_driver = {
+	.probe = simple_mfd_i2c_probe,
+	.driver = {
+		.name = "simple-mfd-i2c",
+		.of_match_table = simple_mfd_i2c_of_match,
+	},
+};
+module_i2c_driver(simple_mfd_i2c_driver);
+
+MODULE_AUTHOR("Michael Walle <michael@walle.cc>");
+MODULE_DESCRIPTION("Simple MFD - I2C driver");
+MODULE_LICENSE("GPL v2");