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, 406 insertions, 0 deletions

diff --git a/drivers/input/touchscreen/elo.c b/drivers/input/touchscreen/elo.c
new file mode 100644
index 000000000..97aeec7ef
--- /dev/null
+++ b/drivers/input/touchscreen/elo.c
@@ -0,0 +1,406 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Elo serial touchscreen driver
+ *
+ * Copyright (c) 2004 Vojtech Pavlik
+ */
+
+
+/*
+ * This driver can handle serial Elo touchscreens using either the Elo standard
+ * 'E271-2210' 10-byte protocol, Elo legacy 'E281A-4002' 6-byte protocol, Elo
+ * legacy 'E271-140' 4-byte protocol and Elo legacy 'E261-280' 3-byte protocol.
+ */
+
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/input.h>
+#include <linux/serio.h>
+#include <linux/ctype.h>
+
+#define DRIVER_DESC	"Elo serial touchscreen driver"
+
+MODULE_AUTHOR("Vojtech Pavlik <vojtech@ucw.cz>");
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL");
+
+/*
+ * Definitions & global arrays.
+ */
+
+#define ELO_MAX_LENGTH		10
+
+#define ELO10_PACKET_LEN	8
+#define ELO10_TOUCH		0x03
+#define ELO10_PRESSURE		0x80
+
+#define ELO10_LEAD_BYTE		'U'
+
+#define ELO10_ID_CMD		'i'
+
+#define ELO10_TOUCH_PACKET	'T'
+#define ELO10_ACK_PACKET	'A'
+#define ELI10_ID_PACKET		'I'
+
+/*
+ * Per-touchscreen data.
+ */
+
+struct elo {
+	struct input_dev *dev;
+	struct serio *serio;
+	struct mutex cmd_mutex;
+	struct completion cmd_done;
+	int id;
+	int idx;
+	unsigned char expected_packet;
+	unsigned char csum;
+	unsigned char data[ELO_MAX_LENGTH];
+	unsigned char response[ELO10_PACKET_LEN];
+	char phys[32];
+};
+
+static void elo_process_data_10(struct elo *elo, unsigned char data)
+{
+	struct input_dev *dev = elo->dev;
+
+	elo->data[elo->idx] = data;
+
+	switch (elo->idx++) {
+	case 0:
+		elo->csum = 0xaa;
+		if (data != ELO10_LEAD_BYTE) {
+			dev_dbg(&elo->serio->dev,
+				"unsynchronized data: 0x%02x\n", data);
+			elo->idx = 0;
+		}
+		break;
+
+	case 9:
+		elo->idx = 0;
+		if (data != elo->csum) {
+			dev_dbg(&elo->serio->dev,
+				"bad checksum: 0x%02x, expected 0x%02x\n",
+				 data, elo->csum);
+			break;
+		}
+		if (elo->data[1] != elo->expected_packet) {
+			if (elo->data[1] != ELO10_TOUCH_PACKET)
+				dev_dbg(&elo->serio->dev,
+					"unexpected packet: 0x%02x\n",
+					 elo->data[1]);
+			break;
+		}
+		if (likely(elo->data[1] == ELO10_TOUCH_PACKET)) {
+			input_report_abs(dev, ABS_X, (elo->data[4] << 8) | elo->data[3]);
+			input_report_abs(dev, ABS_Y, (elo->data[6] << 8) | elo->data[5]);
+			if (elo->data[2] & ELO10_PRESSURE)
+				input_report_abs(dev, ABS_PRESSURE,
+						(elo->data[8] << 8) | elo->data[7]);
+			input_report_key(dev, BTN_TOUCH, elo->data[2] & ELO10_TOUCH);
+			input_sync(dev);
+		} else if (elo->data[1] == ELO10_ACK_PACKET) {
+			if (elo->data[2] == '0')
+				elo->expected_packet = ELO10_TOUCH_PACKET;
+			complete(&elo->cmd_done);
+		} else {
+			memcpy(elo->response, &elo->data[1], ELO10_PACKET_LEN);
+			elo->expected_packet = ELO10_ACK_PACKET;
+		}
+		break;
+	}
+	elo->csum += data;
+}
+
+static void elo_process_data_6(struct elo *elo, unsigned char data)
+{
+	struct input_dev *dev = elo->dev;
+
+	elo->data[elo->idx] = data;
+
+	switch (elo->idx++) {
+
+	case 0:
+		if ((data & 0xc0) != 0xc0)
+			elo->idx = 0;
+		break;
+
+	case 1:
+		if ((data & 0xc0) != 0x80)
+			elo->idx = 0;
+		break;
+
+	case 2:
+		if ((data & 0xc0) != 0x40)
+			elo->idx = 0;
+		break;
+
+	case 3:
+		if (data & 0xc0) {
+			elo->idx = 0;
+			break;
+		}
+
+		input_report_abs(dev, ABS_X, ((elo->data[0] & 0x3f) << 6) | (elo->data[1] & 0x3f));
+		input_report_abs(dev, ABS_Y, ((elo->data[2] & 0x3f) << 6) | (elo->data[3] & 0x3f));
+
+		if (elo->id == 2) {
+			input_report_key(dev, BTN_TOUCH, 1);
+			input_sync(dev);
+			elo->idx = 0;
+		}
+
+		break;
+
+	case 4:
+		if (data) {
+			input_sync(dev);
+			elo->idx = 0;
+		}
+		break;
+
+	case 5:
+		if ((data & 0xf0) == 0) {
+			input_report_abs(dev, ABS_PRESSURE, elo->data[5]);
+			input_report_key(dev, BTN_TOUCH, !!elo->data[5]);
+		}
+		input_sync(dev);
+		elo->idx = 0;
+		break;
+	}
+}
+
+static void elo_process_data_3(struct elo *elo, unsigned char data)
+{
+	struct input_dev *dev = elo->dev;
+
+	elo->data[elo->idx] = data;
+
+	switch (elo->idx++) {
+
+	case 0:
+		if ((data & 0x7f) != 0x01)
+			elo->idx = 0;
+		break;
+	case 2:
+		input_report_key(dev, BTN_TOUCH, !(elo->data[1] & 0x80));
+		input_report_abs(dev, ABS_X, elo->data[1]);
+		input_report_abs(dev, ABS_Y, elo->data[2]);
+		input_sync(dev);
+		elo->idx = 0;
+		break;
+	}
+}
+
+static irqreturn_t elo_interrupt(struct serio *serio,
+		unsigned char data, unsigned int flags)
+{
+	struct elo *elo = serio_get_drvdata(serio);
+
+	switch (elo->id) {
+	case 0:
+		elo_process_data_10(elo, data);
+		break;
+
+	case 1:
+	case 2:
+		elo_process_data_6(elo, data);
+		break;
+
+	case 3:
+		elo_process_data_3(elo, data);
+		break;
+	}
+
+	return IRQ_HANDLED;
+}
+
+static int elo_command_10(struct elo *elo, unsigned char *packet)
+{
+	int error;
+	int i;
+	unsigned char csum = 0xaa + ELO10_LEAD_BYTE;
+
+	guard(mutex)(&elo->cmd_mutex);
+
+	scoped_guard(serio_pause_rx, elo->serio) {
+		elo->expected_packet = toupper(packet[0]);
+		init_completion(&elo->cmd_done);
+	}
+
+	error = serio_write(elo->serio, ELO10_LEAD_BYTE);
+	if (error)
+		return error;
+
+	for (i = 0; i < ELO10_PACKET_LEN; i++) {
+		csum += packet[i];
+		error = serio_write(elo->serio, packet[i]);
+		if (error)
+			return error;
+	}
+
+	error = serio_write(elo->serio, csum);
+	if (error)
+		return error;
+
+	wait_for_completion_timeout(&elo->cmd_done, HZ);
+
+	if (elo->expected_packet != ELO10_TOUCH_PACKET)
+		return -EIO;
+
+	/* We are back in reporting mode, the command was ACKed */
+	memcpy(packet, elo->response, ELO10_PACKET_LEN);
+	return 0;
+}
+
+static int elo_setup_10(struct elo *elo)
+{
+	static const char * const elo_types[] = { "Accu", "Dura", "Intelli", "Carroll" };
+	struct input_dev *dev = elo->dev;
+	unsigned char packet[ELO10_PACKET_LEN] = { ELO10_ID_CMD };
+
+	if (elo_command_10(elo, packet))
+		return -1;
+
+	dev->id.version = (packet[5] << 8) | packet[4];
+
+	input_set_abs_params(dev, ABS_X, 96, 4000, 0, 0);
+	input_set_abs_params(dev, ABS_Y, 96, 4000, 0, 0);
+	if (packet[3] & ELO10_PRESSURE)
+		input_set_abs_params(dev, ABS_PRESSURE, 0, 255, 0, 0);
+
+	dev_info(&elo->serio->dev,
+		 "%sTouch touchscreen, fw: %02x.%02x, features: 0x%02x, controller: 0x%02x\n",
+		 elo_types[(packet[1] - '0') & 0x03],
+		 packet[5], packet[4], packet[3], packet[7]);
+
+	return 0;
+}
+
+/*
+ * elo_disconnect() is the opposite of elo_connect()
+ */
+
+static void elo_disconnect(struct serio *serio)
+{
+	struct elo *elo = serio_get_drvdata(serio);
+
+	input_get_device(elo->dev);
+	input_unregister_device(elo->dev);
+	serio_close(serio);
+	serio_set_drvdata(serio, NULL);
+	input_put_device(elo->dev);
+	kfree(elo);
+}
+
+/*
+ * elo_connect() is the routine that is called when someone adds a
+ * new serio device that supports Gunze protocol and registers it as
+ * an input device.
+ */
+
+static int elo_connect(struct serio *serio, struct serio_driver *drv)
+{
+	struct elo *elo;
+	struct input_dev *input_dev;
+	int err;
+
+	elo = kzalloc_obj(*elo);
+	input_dev = input_allocate_device();
+	if (!elo || !input_dev) {
+		err = -ENOMEM;
+		goto fail1;
+	}
+
+	elo->serio = serio;
+	elo->id = serio->id.id;
+	elo->dev = input_dev;
+	elo->expected_packet = ELO10_TOUCH_PACKET;
+	mutex_init(&elo->cmd_mutex);
+	init_completion(&elo->cmd_done);
+	scnprintf(elo->phys, sizeof(elo->phys), "%s/input0", serio->phys);
+
+	input_dev->name = "Elo Serial TouchScreen";
+	input_dev->phys = elo->phys;
+	input_dev->id.bustype = BUS_RS232;
+	input_dev->id.vendor = SERIO_ELO;
+	input_dev->id.product = elo->id;
+	input_dev->id.version = 0x0100;
+	input_dev->dev.parent = &serio->dev;
+
+	input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);
+	input_dev->keybit[BIT_WORD(BTN_TOUCH)] = BIT_MASK(BTN_TOUCH);
+
+	serio_set_drvdata(serio, elo);
+	err = serio_open(serio, drv);
+	if (err)
+		goto fail2;
+
+	switch (elo->id) {
+
+	case 0: /* 10-byte protocol */
+		if (elo_setup_10(elo)) {
+			err = -EIO;
+			goto fail3;
+		}
+
+		break;
+
+	case 1: /* 6-byte protocol */
+		input_set_abs_params(input_dev, ABS_PRESSURE, 0, 15, 0, 0);
+		fallthrough;
+
+	case 2: /* 4-byte protocol */
+		input_set_abs_params(input_dev, ABS_X, 96, 4000, 0, 0);
+		input_set_abs_params(input_dev, ABS_Y, 96, 4000, 0, 0);
+		break;
+
+	case 3: /* 3-byte protocol */
+		input_set_abs_params(input_dev, ABS_X, 0, 255, 0, 0);
+		input_set_abs_params(input_dev, ABS_Y, 0, 255, 0, 0);
+		break;
+	}
+
+	err = input_register_device(elo->dev);
+	if (err)
+		goto fail3;
+
+	return 0;
+
+ fail3: serio_close(serio);
+ fail2:	serio_set_drvdata(serio, NULL);
+ fail1:	input_free_device(input_dev);
+	kfree(elo);
+	return err;
+}
+
+/*
+ * The serio driver structure.
+ */
+
+static const struct serio_device_id elo_serio_ids[] = {
+	{
+		.type	= SERIO_RS232,
+		.proto	= SERIO_ELO,
+		.id	= SERIO_ANY,
+		.extra	= SERIO_ANY,
+	},
+	{ 0 }
+};
+
+MODULE_DEVICE_TABLE(serio, elo_serio_ids);
+
+static struct serio_driver elo_drv = {
+	.driver		= {
+		.name	= "elo",
+	},
+	.description	= DRIVER_DESC,
+	.id_table	= elo_serio_ids,
+	.interrupt	= elo_interrupt,
+	.connect	= elo_connect,
+	.disconnect	= elo_disconnect,
+};
+
+module_serio_driver(elo_drv);