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, 153 insertions, 0 deletions

diff --git a/drivers/input/mouse/maplemouse.c b/drivers/input/mouse/maplemouse.c
new file mode 100644
index 000000000..0c8f7d1b0
--- /dev/null
+++ b/drivers/input/mouse/maplemouse.c
@@ -0,0 +1,153 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *	SEGA Dreamcast mouse driver
+ *	Based on drivers/usb/usbmouse.c
+ *
+ *	Copyright (c) Yaegashi Takeshi, 2001
+ *	Copyright (c) Adrian McMenamin, 2008 - 2009
+ */
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/input.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/timer.h>
+#include <linux/maple.h>
+
+MODULE_AUTHOR("Adrian McMenamin <adrian@mcmen.demon.co.uk>");
+MODULE_DESCRIPTION("SEGA Dreamcast mouse driver");
+MODULE_LICENSE("GPL");
+
+struct dc_mouse {
+	struct input_dev *dev;
+	struct maple_device *mdev;
+};
+
+static void dc_mouse_callback(struct mapleq *mq)
+{
+	int buttons, relx, rely, relz;
+	struct maple_device *mapledev = mq->dev;
+	struct dc_mouse *mse = maple_get_drvdata(mapledev);
+	struct input_dev *dev = mse->dev;
+	unsigned char *res = mq->recvbuf->buf;
+
+	buttons = ~res[8];
+	relx = *(unsigned short *)(res + 12) - 512;
+	rely = *(unsigned short *)(res + 14) - 512;
+	relz = *(unsigned short *)(res + 16) - 512;
+
+	input_report_key(dev, BTN_LEFT,   buttons & 4);
+	input_report_key(dev, BTN_MIDDLE, buttons & 9);
+	input_report_key(dev, BTN_RIGHT,  buttons & 2);
+	input_report_rel(dev, REL_X,      relx);
+	input_report_rel(dev, REL_Y,      rely);
+	input_report_rel(dev, REL_WHEEL,  relz);
+	input_sync(dev);
+}
+
+static int dc_mouse_open(struct input_dev *dev)
+{
+	struct dc_mouse *mse = input_get_drvdata(dev);
+
+	maple_getcond_callback(mse->mdev, dc_mouse_callback, HZ/50,
+		MAPLE_FUNC_MOUSE);
+
+	return 0;
+}
+
+static void dc_mouse_close(struct input_dev *dev)
+{
+	struct dc_mouse *mse = input_get_drvdata(dev);
+
+	maple_getcond_callback(mse->mdev, dc_mouse_callback, 0,
+		MAPLE_FUNC_MOUSE);
+}
+
+/* allow the mouse to be used */
+static int probe_maple_mouse(struct device *dev)
+{
+	struct maple_device *mdev = to_maple_dev(dev);
+	struct maple_driver *mdrv = to_maple_driver(dev->driver);
+	int error;
+	struct input_dev *input_dev;
+	struct dc_mouse *mse;
+
+	mse = kzalloc_obj(*mse);
+	if (!mse) {
+		error = -ENOMEM;
+		goto fail;
+	}
+
+	input_dev = input_allocate_device();
+	if (!input_dev) {
+		error = -ENOMEM;
+		goto fail_nomem;
+	}
+
+	mse->dev = input_dev;
+	mse->mdev = mdev;
+
+	maple_set_drvdata(mdev, mse);
+
+	input_set_drvdata(input_dev, mse);
+	input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_REL);
+	input_dev->keybit[BIT_WORD(BTN_MOUSE)] = BIT_MASK(BTN_LEFT) |
+		BIT_MASK(BTN_RIGHT) | BIT_MASK(BTN_MIDDLE);
+	input_dev->relbit[0] = BIT_MASK(REL_X) | BIT_MASK(REL_Y) |
+		BIT_MASK(REL_WHEEL);
+	input_dev->open = dc_mouse_open;
+	input_dev->close = dc_mouse_close;
+	input_dev->name = mdev->product_name;
+	input_dev->id.bustype = BUS_HOST;
+	error =	input_register_device(input_dev);
+	if (error)
+		goto fail_register;
+
+	mdev->driver = mdrv;
+
+	return error;
+
+fail_register:
+	input_free_device(input_dev);
+	maple_set_drvdata(mdev, NULL);
+fail_nomem:
+	kfree(mse);
+fail:
+	return error;
+}
+
+static int remove_maple_mouse(struct device *dev)
+{
+	struct maple_device *mdev = to_maple_dev(dev);
+	struct dc_mouse *mse = maple_get_drvdata(mdev);
+
+	mdev->callback = NULL;
+	input_unregister_device(mse->dev);
+	maple_set_drvdata(mdev, NULL);
+	kfree(mse);
+
+	return 0;
+}
+
+static struct maple_driver dc_mouse_driver = {
+	.function =	MAPLE_FUNC_MOUSE,
+	.drv = {
+		.name = "Dreamcast_mouse",
+		.probe = probe_maple_mouse,
+		.remove = remove_maple_mouse,
+	},
+};
+
+static int __init dc_mouse_init(void)
+{
+	return maple_driver_register(&dc_mouse_driver);
+}
+
+static void __exit dc_mouse_exit(void)
+{
+	maple_driver_unregister(&dc_mouse_driver);
+}
+
+module_init(dc_mouse_init);
+module_exit(dc_mouse_exit);