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, 150 insertions, 0 deletions

diff --git a/drivers/input/mouse/amimouse.c b/drivers/input/mouse/amimouse.c
new file mode 100644
index 000000000..d203c2a6c
--- /dev/null
+++ b/drivers/input/mouse/amimouse.c
@@ -0,0 +1,150 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  Amiga mouse driver for Linux/m68k
+ *
+ *  Copyright (c) 2000-2002 Vojtech Pavlik
+ *
+ *  Based on the work of:
+ *	Michael Rausch		James Banks
+ *	Matther Dillon		David Giller
+ *	Nathan Laredo		Linus Torvalds
+ *	Johan Myreen		Jes Sorensen
+ *	Russell King
+ */
+
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/input.h>
+#include <linux/interrupt.h>
+#include <linux/platform_device.h>
+
+#include <asm/irq.h>
+#include <asm/setup.h>
+#include <linux/uaccess.h>
+#include <asm/amigahw.h>
+#include <asm/amigaints.h>
+
+MODULE_AUTHOR("Vojtech Pavlik <vojtech@ucw.cz>");
+MODULE_DESCRIPTION("Amiga mouse driver");
+MODULE_LICENSE("GPL");
+
+static int amimouse_lastx, amimouse_lasty;
+
+static irqreturn_t amimouse_interrupt(int irq, void *data)
+{
+	struct input_dev *dev = data;
+	unsigned short joy0dat, potgor;
+	int nx, ny, dx, dy;
+
+	joy0dat = amiga_custom.joy0dat;
+
+	nx = joy0dat & 0xff;
+	ny = joy0dat >> 8;
+
+	dx = nx - amimouse_lastx;
+	dy = ny - amimouse_lasty;
+
+	if (dx < -127) dx = (256 + nx) - amimouse_lastx;
+	if (dx >  127) dx = (nx - 256) - amimouse_lastx;
+	if (dy < -127) dy = (256 + ny) - amimouse_lasty;
+	if (dy >  127) dy = (ny - 256) - amimouse_lasty;
+
+	amimouse_lastx = nx;
+	amimouse_lasty = ny;
+
+	potgor = amiga_custom.potgor;
+
+	input_report_rel(dev, REL_X, dx);
+	input_report_rel(dev, REL_Y, dy);
+
+	input_report_key(dev, BTN_LEFT,   ciaa.pra & 0x40);
+	input_report_key(dev, BTN_MIDDLE, potgor & 0x0100);
+	input_report_key(dev, BTN_RIGHT,  potgor & 0x0400);
+
+	input_sync(dev);
+
+	return IRQ_HANDLED;
+}
+
+static int amimouse_open(struct input_dev *dev)
+{
+	unsigned short joy0dat;
+	int error;
+
+	joy0dat = amiga_custom.joy0dat;
+
+	amimouse_lastx = joy0dat & 0xff;
+	amimouse_lasty = joy0dat >> 8;
+
+	error = request_irq(IRQ_AMIGA_VERTB, amimouse_interrupt, 0, "amimouse",
+			    dev);
+	if (error)
+		dev_err(&dev->dev, "Can't allocate irq %d\n", IRQ_AMIGA_VERTB);
+
+	return error;
+}
+
+static void amimouse_close(struct input_dev *dev)
+{
+	free_irq(IRQ_AMIGA_VERTB, dev);
+}
+
+static int __init amimouse_probe(struct platform_device *pdev)
+{
+	int err;
+	struct input_dev *dev;
+
+	dev = input_allocate_device();
+	if (!dev)
+		return -ENOMEM;
+
+	dev->name = pdev->name;
+	dev->phys = "amimouse/input0";
+	dev->id.bustype = BUS_AMIGA;
+	dev->id.vendor = 0x0001;
+	dev->id.product = 0x0002;
+	dev->id.version = 0x0100;
+
+	dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_REL);
+	dev->relbit[0] = BIT_MASK(REL_X) | BIT_MASK(REL_Y);
+	dev->keybit[BIT_WORD(BTN_LEFT)] = BIT_MASK(BTN_LEFT) |
+		BIT_MASK(BTN_MIDDLE) | BIT_MASK(BTN_RIGHT);
+	dev->open = amimouse_open;
+	dev->close = amimouse_close;
+	dev->dev.parent = &pdev->dev;
+
+	err = input_register_device(dev);
+	if (err) {
+		input_free_device(dev);
+		return err;
+	}
+
+	platform_set_drvdata(pdev, dev);
+
+	return 0;
+}
+
+static void __exit amimouse_remove(struct platform_device *pdev)
+{
+	struct input_dev *dev = platform_get_drvdata(pdev);
+
+	input_unregister_device(dev);
+}
+
+/*
+ * amimouse_remove() lives in .exit.text. For drivers registered via
+ * module_platform_driver_probe() this is ok because they cannot get unbound at
+ * runtime. So mark the driver struct with __refdata to prevent modpost
+ * triggering a section mismatch warning.
+ */
+static struct platform_driver amimouse_driver __refdata = {
+	.remove = __exit_p(amimouse_remove),
+	.driver   = {
+		.name	= "amiga-mouse",
+	},
+};
+
+module_platform_driver_probe(amimouse_driver, amimouse_probe);
+
+MODULE_ALIAS("platform:amiga-mouse");