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, 269 insertions, 0 deletions

diff --git a/drivers/iio/frequency/admfm2000.c b/drivers/iio/frequency/admfm2000.c
new file mode 100644
index 000000000..0405b53c5
--- /dev/null
+++ b/drivers/iio/frequency/admfm2000.c
@@ -0,0 +1,269 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * ADMFM2000 Dual Microwave Down Converter
+ *
+ * Copyright 2024 Analog Devices Inc.
+ */
+
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/gpio/consumer.h>
+#include <linux/iio/iio.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+
+#define ADMFM2000_MIXER_MODE		0
+#define ADMFM2000_DIRECT_IF_MODE	1
+#define ADMFM2000_DSA_GPIOS		5
+#define ADMFM2000_MODE_GPIOS		2
+#define ADMFM2000_MAX_GAIN		0
+#define ADMFM2000_MIN_GAIN		-31000
+#define ADMFM2000_DEFAULT_GAIN		-0x20
+
+struct admfm2000_state {
+	struct mutex			lock; /* protect sensor state */
+	struct gpio_desc		*sw1_ch[2];
+	struct gpio_desc		*sw2_ch[2];
+	struct gpio_desc		*dsa1_gpios[5];
+	struct gpio_desc		*dsa2_gpios[5];
+	u32				gain[2];
+};
+
+static int admfm2000_mode(struct iio_dev *indio_dev, u32 chan, u32 mode)
+{
+	struct admfm2000_state *st = iio_priv(indio_dev);
+	int i;
+
+	switch (mode) {
+	case ADMFM2000_MIXER_MODE:
+		for (i = 0; i < ADMFM2000_MODE_GPIOS; i++) {
+			gpiod_set_value_cansleep(st->sw1_ch[i], (chan == 0) ? 1 : 0);
+			gpiod_set_value_cansleep(st->sw2_ch[i], (chan == 0) ? 0 : 1);
+		}
+		return 0;
+	case ADMFM2000_DIRECT_IF_MODE:
+		for (i = 0; i < ADMFM2000_MODE_GPIOS; i++) {
+			gpiod_set_value_cansleep(st->sw1_ch[i], (chan == 0) ? 0 : 1);
+			gpiod_set_value_cansleep(st->sw2_ch[i], (chan == 0) ? 1 : 0);
+		}
+		return 0;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int admfm2000_attenuation(struct iio_dev *indio_dev, u32 chan, u32 value)
+{
+	struct admfm2000_state *st = iio_priv(indio_dev);
+	int i;
+
+	switch (chan) {
+	case 0:
+		for (i = 0; i < ADMFM2000_DSA_GPIOS; i++)
+			gpiod_set_value_cansleep(st->dsa1_gpios[i], value & (1 << i));
+		return 0;
+	case 1:
+		for (i = 0; i < ADMFM2000_DSA_GPIOS; i++)
+			gpiod_set_value_cansleep(st->dsa2_gpios[i], value & (1 << i));
+		return 0;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int admfm2000_read_raw(struct iio_dev *indio_dev,
+			      struct iio_chan_spec const *chan, int *val,
+			      int *val2, long mask)
+{
+	struct admfm2000_state *st = iio_priv(indio_dev);
+	int gain;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_HARDWAREGAIN:
+		mutex_lock(&st->lock);
+		gain = ~(st->gain[chan->channel]) * -1000;
+		*val = gain / 1000;
+		*val2 = (gain % 1000) * 1000;
+		mutex_unlock(&st->lock);
+
+		return IIO_VAL_INT_PLUS_MICRO_DB;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int admfm2000_write_raw(struct iio_dev *indio_dev,
+			       struct iio_chan_spec const *chan, int val,
+			       int val2, long mask)
+{
+	struct admfm2000_state *st = iio_priv(indio_dev);
+	int gain, ret;
+
+	if (val < 0)
+		gain = (val * 1000) - (val2 / 1000);
+	else
+		gain = (val * 1000) + (val2 / 1000);
+
+	if (gain > ADMFM2000_MAX_GAIN || gain < ADMFM2000_MIN_GAIN)
+		return -EINVAL;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_HARDWAREGAIN:
+		mutex_lock(&st->lock);
+		st->gain[chan->channel] = ~((abs(gain) / 1000) & 0x1F);
+
+		ret = admfm2000_attenuation(indio_dev, chan->channel,
+					    st->gain[chan->channel]);
+		mutex_unlock(&st->lock);
+		return ret;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int admfm2000_write_raw_get_fmt(struct iio_dev *indio_dev,
+				       struct iio_chan_spec const *chan,
+				       long mask)
+{
+	switch (mask) {
+	case IIO_CHAN_INFO_HARDWAREGAIN:
+		return IIO_VAL_INT_PLUS_MICRO_DB;
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct iio_info admfm2000_info = {
+	.read_raw = &admfm2000_read_raw,
+	.write_raw = &admfm2000_write_raw,
+	.write_raw_get_fmt = &admfm2000_write_raw_get_fmt,
+};
+
+#define ADMFM2000_CHAN(_channel) {					\
+	.type = IIO_VOLTAGE,						\
+	.output = 1,							\
+	.indexed = 1,							\
+	.channel = _channel,						\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_HARDWAREGAIN),		\
+}
+
+static const struct iio_chan_spec admfm2000_channels[] = {
+	ADMFM2000_CHAN(0),
+	ADMFM2000_CHAN(1),
+};
+
+static int admfm2000_channel_config(struct admfm2000_state *st,
+				    struct iio_dev *indio_dev)
+{
+	struct platform_device *pdev = to_platform_device(indio_dev->dev.parent);
+	struct device *dev = &pdev->dev;
+	struct gpio_desc **dsa;
+	struct gpio_desc **sw;
+	int ret, i;
+	bool mode;
+	u32 reg;
+
+	device_for_each_child_node_scoped(dev, child) {
+		ret = fwnode_property_read_u32(child, "reg", &reg);
+		if (ret)
+			return dev_err_probe(dev, ret,
+					     "Failed to get reg property\n");
+
+		if (reg >= indio_dev->num_channels)
+			return dev_err_probe(dev, -EINVAL, "reg bigger than: %d\n",
+					     indio_dev->num_channels);
+
+		if (fwnode_property_present(child, "adi,mixer-mode"))
+			mode = ADMFM2000_MIXER_MODE;
+		else
+			mode = ADMFM2000_DIRECT_IF_MODE;
+
+		switch (reg) {
+		case 0:
+			sw = st->sw1_ch;
+			dsa = st->dsa1_gpios;
+			break;
+		case 1:
+			sw = st->sw2_ch;
+			dsa = st->dsa2_gpios;
+			break;
+		default:
+			return -EINVAL;
+		}
+
+		for (i = 0; i < ADMFM2000_MODE_GPIOS; i++) {
+			sw[i] = devm_fwnode_gpiod_get_index(dev, child, "switch",
+							    i, GPIOD_OUT_LOW, NULL);
+			if (IS_ERR(sw[i]))
+				return dev_err_probe(dev, PTR_ERR(sw[i]),
+						     "Failed to get gpios\n");
+		}
+
+		for (i = 0; i < ADMFM2000_DSA_GPIOS; i++) {
+			dsa[i] = devm_fwnode_gpiod_get_index(dev, child,
+							     "attenuation", i,
+							     GPIOD_OUT_LOW, NULL);
+			if (IS_ERR(dsa[i]))
+				return dev_err_probe(dev, PTR_ERR(dsa[i]),
+						     "Failed to get gpios\n");
+		}
+
+		ret = admfm2000_mode(indio_dev, reg, mode);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+static int admfm2000_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct admfm2000_state *st;
+	struct iio_dev *indio_dev;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*st));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	st = iio_priv(indio_dev);
+
+	indio_dev->name = "admfm2000";
+	indio_dev->num_channels = ARRAY_SIZE(admfm2000_channels);
+	indio_dev->channels = admfm2000_channels;
+	indio_dev->info = &admfm2000_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+
+	st->gain[0] = ADMFM2000_DEFAULT_GAIN;
+	st->gain[1] = ADMFM2000_DEFAULT_GAIN;
+
+	mutex_init(&st->lock);
+
+	ret = admfm2000_channel_config(st, indio_dev);
+	if (ret)
+		return ret;
+
+	return devm_iio_device_register(dev, indio_dev);
+}
+
+static const struct of_device_id admfm2000_of_match[] = {
+	{ .compatible = "adi,admfm2000" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, admfm2000_of_match);
+
+static struct platform_driver admfm2000_driver = {
+	.driver = {
+		.name = "admfm2000",
+		.of_match_table = admfm2000_of_match,
+	},
+	.probe = admfm2000_probe,
+};
+module_platform_driver(admfm2000_driver);
+
+MODULE_AUTHOR("Kim Seer Paller <kimseer.paller@analog.com>");
+MODULE_DESCRIPTION("ADMFM2000 Dual Microwave Down Converter");
+MODULE_LICENSE("GPL");