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, 184 insertions, 0 deletions

diff --git a/drivers/input/touchscreen/hampshire.c b/drivers/input/touchscreen/hampshire.c
new file mode 100644
index 000000000..394ae8c88
--- /dev/null
+++ b/drivers/input/touchscreen/hampshire.c
@@ -0,0 +1,184 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Hampshire serial touchscreen driver
+ *
+ * Copyright (c) 2010 Adam Bennett
+ * Based on the dynapro driver (c) Tias Guns
+ */
+
+
+/*
+ * 2010/04/08 Adam Bennett <abennett72@gmail.com>
+ *   Copied dynapro.c and edited for Hampshire 4-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>
+
+#define DRIVER_DESC	"Hampshire serial touchscreen driver"
+
+MODULE_AUTHOR("Adam Bennett <abennett72@gmail.com>");
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL");
+
+/*
+ * Definitions & global arrays.
+ */
+
+#define HAMPSHIRE_FORMAT_TOUCH_BIT 0x40
+#define HAMPSHIRE_FORMAT_LENGTH 4
+#define HAMPSHIRE_RESPONSE_BEGIN_BYTE 0x80
+
+#define HAMPSHIRE_MIN_XC 0
+#define HAMPSHIRE_MAX_XC 0x1000
+#define HAMPSHIRE_MIN_YC 0
+#define HAMPSHIRE_MAX_YC 0x1000
+
+#define HAMPSHIRE_GET_XC(data) (((data[3] & 0x0c) >> 2) | (data[1] << 2) | ((data[0] & 0x38) << 6))
+#define HAMPSHIRE_GET_YC(data) ((data[3] & 0x03) | (data[2] << 2) | ((data[0] & 0x07) << 9))
+#define HAMPSHIRE_GET_TOUCHED(data) (HAMPSHIRE_FORMAT_TOUCH_BIT & data[0])
+
+/*
+ * Per-touchscreen data.
+ */
+
+struct hampshire {
+	struct input_dev *dev;
+	struct serio *serio;
+	int idx;
+	unsigned char data[HAMPSHIRE_FORMAT_LENGTH];
+	char phys[32];
+};
+
+static void hampshire_process_data(struct hampshire *phampshire)
+{
+	struct input_dev *dev = phampshire->dev;
+
+	if (HAMPSHIRE_FORMAT_LENGTH == ++phampshire->idx) {
+		input_report_abs(dev, ABS_X, HAMPSHIRE_GET_XC(phampshire->data));
+		input_report_abs(dev, ABS_Y, HAMPSHIRE_GET_YC(phampshire->data));
+		input_report_key(dev, BTN_TOUCH,
+				 HAMPSHIRE_GET_TOUCHED(phampshire->data));
+		input_sync(dev);
+
+		phampshire->idx = 0;
+	}
+}
+
+static irqreturn_t hampshire_interrupt(struct serio *serio,
+		unsigned char data, unsigned int flags)
+{
+	struct hampshire *phampshire = serio_get_drvdata(serio);
+
+	phampshire->data[phampshire->idx] = data;
+
+	if (HAMPSHIRE_RESPONSE_BEGIN_BYTE & phampshire->data[0])
+		hampshire_process_data(phampshire);
+	else
+		dev_dbg(&serio->dev, "unknown/unsynchronized data: %x\n",
+			phampshire->data[0]);
+
+	return IRQ_HANDLED;
+}
+
+static void hampshire_disconnect(struct serio *serio)
+{
+	struct hampshire *phampshire = serio_get_drvdata(serio);
+
+	input_get_device(phampshire->dev);
+	input_unregister_device(phampshire->dev);
+	serio_close(serio);
+	serio_set_drvdata(serio, NULL);
+	input_put_device(phampshire->dev);
+	kfree(phampshire);
+}
+
+/*
+ * hampshire_connect() is the routine that is called when someone adds a
+ * new serio device that supports hampshire protocol and registers it as
+ * an input device. This is usually accomplished using inputattach.
+ */
+
+static int hampshire_connect(struct serio *serio, struct serio_driver *drv)
+{
+	struct hampshire *phampshire;
+	struct input_dev *input_dev;
+	int err;
+
+	phampshire = kzalloc_obj(*phampshire);
+	input_dev = input_allocate_device();
+	if (!phampshire || !input_dev) {
+		err = -ENOMEM;
+		goto fail1;
+	}
+
+	phampshire->serio = serio;
+	phampshire->dev = input_dev;
+	scnprintf(phampshire->phys, sizeof(phampshire->phys),
+		  "%s/input0", serio->phys);
+
+	input_dev->name = "Hampshire Serial TouchScreen";
+	input_dev->phys = phampshire->phys;
+	input_dev->id.bustype = BUS_RS232;
+	input_dev->id.vendor = SERIO_HAMPSHIRE;
+	input_dev->id.product = 0;
+	input_dev->id.version = 0x0001;
+	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);
+	input_set_abs_params(phampshire->dev, ABS_X,
+			     HAMPSHIRE_MIN_XC, HAMPSHIRE_MAX_XC, 0, 0);
+	input_set_abs_params(phampshire->dev, ABS_Y,
+			     HAMPSHIRE_MIN_YC, HAMPSHIRE_MAX_YC, 0, 0);
+
+	serio_set_drvdata(serio, phampshire);
+
+	err = serio_open(serio, drv);
+	if (err)
+		goto fail2;
+
+	err = input_register_device(phampshire->dev);
+	if (err)
+		goto fail3;
+
+	return 0;
+
+ fail3:	serio_close(serio);
+ fail2:	serio_set_drvdata(serio, NULL);
+ fail1:	input_free_device(input_dev);
+	kfree(phampshire);
+	return err;
+}
+
+/*
+ * The serio driver structure.
+ */
+
+static const struct serio_device_id hampshire_serio_ids[] = {
+	{
+		.type	= SERIO_RS232,
+		.proto	= SERIO_HAMPSHIRE,
+		.id	= SERIO_ANY,
+		.extra	= SERIO_ANY,
+	},
+	{ 0 }
+};
+
+MODULE_DEVICE_TABLE(serio, hampshire_serio_ids);
+
+static struct serio_driver hampshire_drv = {
+	.driver		= {
+		.name	= "hampshire",
+	},
+	.description	= DRIVER_DESC,
+	.id_table	= hampshire_serio_ids,
+	.interrupt	= hampshire_interrupt,
+	.connect	= hampshire_connect,
+	.disconnect	= hampshire_disconnect,
+};
+
+module_serio_driver(hampshire_drv);