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, 191 insertions, 0 deletions

diff --git a/drivers/input/joystick/stinger.c b/drivers/input/joystick/stinger.c
new file mode 100644
index 000000000..011f9b137
--- /dev/null
+++ b/drivers/input/joystick/stinger.c
@@ -0,0 +1,191 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Copyright (c) 2000-2001 Vojtech Pavlik
+ *  Copyright (c) 2000 Mark Fletcher
+ */
+
+/*
+ * Gravis Stinger gamepad driver for Linux
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/input.h>
+#include <linux/serio.h>
+
+#define DRIVER_DESC	"Gravis Stinger gamepad driver"
+
+MODULE_AUTHOR("Vojtech Pavlik <vojtech@ucw.cz>");
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL");
+
+/*
+ * Constants.
+ */
+
+#define STINGER_MAX_LENGTH 8
+
+/*
+ * Per-Stinger data.
+ */
+
+struct stinger {
+	struct input_dev *dev;
+	int idx;
+	unsigned char data[STINGER_MAX_LENGTH];
+	char phys[32];
+};
+
+/*
+ * stinger_process_packet() decodes packets the driver receives from the
+ * Stinger. It updates the data accordingly.
+ */
+
+static void stinger_process_packet(struct stinger *stinger)
+{
+	struct input_dev *dev = stinger->dev;
+	unsigned char *data = stinger->data;
+
+	if (!stinger->idx) return;
+
+	input_report_key(dev, BTN_A,	  ((data[0] & 0x20) >> 5));
+	input_report_key(dev, BTN_B,	  ((data[0] & 0x10) >> 4));
+	input_report_key(dev, BTN_C,	  ((data[0] & 0x08) >> 3));
+	input_report_key(dev, BTN_X,	  ((data[0] & 0x04) >> 2));
+	input_report_key(dev, BTN_Y,	  ((data[3] & 0x20) >> 5));
+	input_report_key(dev, BTN_Z,	  ((data[3] & 0x10) >> 4));
+	input_report_key(dev, BTN_TL,     ((data[3] & 0x08) >> 3));
+	input_report_key(dev, BTN_TR,     ((data[3] & 0x04) >> 2));
+	input_report_key(dev, BTN_SELECT, ((data[3] & 0x02) >> 1));
+	input_report_key(dev, BTN_START,   (data[3] & 0x01));
+
+	input_report_abs(dev, ABS_X, (data[1] & 0x3F) - ((data[0] & 0x01) << 6));
+	input_report_abs(dev, ABS_Y, ((data[0] & 0x02) << 5) - (data[2] & 0x3F));
+
+	input_sync(dev);
+
+	return;
+}
+
+/*
+ * stinger_interrupt() is called by the low level driver when characters
+ * are ready for us. We then buffer them for further processing, or call the
+ * packet processing routine.
+ */
+
+static irqreturn_t stinger_interrupt(struct serio *serio,
+	unsigned char data, unsigned int flags)
+{
+	struct stinger *stinger = serio_get_drvdata(serio);
+
+	/* All Stinger packets are 4 bytes */
+
+	if (stinger->idx < STINGER_MAX_LENGTH)
+		stinger->data[stinger->idx++] = data;
+
+	if (stinger->idx == 4) {
+		stinger_process_packet(stinger);
+		stinger->idx = 0;
+	}
+
+	return IRQ_HANDLED;
+}
+
+/*
+ * stinger_disconnect() is the opposite of stinger_connect()
+ */
+
+static void stinger_disconnect(struct serio *serio)
+{
+	struct stinger *stinger = serio_get_drvdata(serio);
+
+	serio_close(serio);
+	serio_set_drvdata(serio, NULL);
+	input_unregister_device(stinger->dev);
+	kfree(stinger);
+}
+
+/*
+ * stinger_connect() is the routine that is called when someone adds a
+ * new serio device that supports Stinger protocol and registers it as
+ * an input device.
+ */
+
+static int stinger_connect(struct serio *serio, struct serio_driver *drv)
+{
+	struct stinger *stinger;
+	struct input_dev *input_dev;
+	int err = -ENOMEM;
+
+	stinger = kmalloc_obj(*stinger);
+	input_dev = input_allocate_device();
+	if (!stinger || !input_dev)
+		goto fail1;
+
+	stinger->dev = input_dev;
+	snprintf(stinger->phys, sizeof(stinger->phys), "%s/serio0", serio->phys);
+
+	input_dev->name = "Gravis Stinger";
+	input_dev->phys = stinger->phys;
+	input_dev->id.bustype = BUS_RS232;
+	input_dev->id.vendor = SERIO_STINGER;
+	input_dev->id.product = 0x0001;
+	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_A)] = BIT_MASK(BTN_A) | BIT_MASK(BTN_B) |
+		BIT_MASK(BTN_C) | BIT_MASK(BTN_X) | BIT_MASK(BTN_Y) |
+		BIT_MASK(BTN_Z) | BIT_MASK(BTN_TL) | BIT_MASK(BTN_TR) |
+		BIT_MASK(BTN_START) | BIT_MASK(BTN_SELECT);
+	input_set_abs_params(input_dev, ABS_X, -64, 64, 0, 4);
+	input_set_abs_params(input_dev, ABS_Y, -64, 64, 0, 4);
+
+	serio_set_drvdata(serio, stinger);
+
+	err = serio_open(serio, drv);
+	if (err)
+		goto fail2;
+
+	err = input_register_device(stinger->dev);
+	if (err)
+		goto fail3;
+
+	return 0;
+
+ fail3:	serio_close(serio);
+ fail2:	serio_set_drvdata(serio, NULL);
+ fail1:	input_free_device(input_dev);
+	kfree(stinger);
+	return err;
+}
+
+/*
+ * The serio driver structure.
+ */
+
+static const struct serio_device_id stinger_serio_ids[] = {
+	{
+		.type	= SERIO_RS232,
+		.proto	= SERIO_STINGER,
+		.id	= SERIO_ANY,
+		.extra	= SERIO_ANY,
+	},
+	{ 0 }
+};
+
+MODULE_DEVICE_TABLE(serio, stinger_serio_ids);
+
+static struct serio_driver stinger_drv = {
+	.driver		= {
+		.name	= "stinger",
+	},
+	.description	= DRIVER_DESC,
+	.id_table	= stinger_serio_ids,
+	.interrupt	= stinger_interrupt,
+	.connect	= stinger_connect,
+	.disconnect	= stinger_disconnect,
+};
+
+module_serio_driver(stinger_drv);