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, 117 insertions, 0 deletions

diff --git a/drivers/hid/hid-hyperx.c b/drivers/hid/hid-hyperx.c
new file mode 100644
index 000000000..18d2dc24c
--- /dev/null
+++ b/drivers/hid/hid-hyperx.c
@@ -0,0 +1,117 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  HID driver for the HyperX QuadCast 2 microphone
+ *
+ *  The tap-to-mute button is handled entirely in the device firmware: it gates
+ *  the audio internally and does not send the Telephony "Phone Mute" usage its
+ *  own report descriptor advertises.  The resulting mute state is only reported
+ *  through a vendor-defined collection, which hid-input cannot map, so the
+ *  button is invisible to userspace.
+ *
+ *  Copyright (c) 2026 Benjamin Blume <benjaminblume@posteo.de>
+ */
+
+#include <linux/hid.h>
+#include <linux/input.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+#define HYPERX_QC2_REPORT_ID	0x77
+#define HYPERX_QC2_EVENT_MUTE	0x06
+#define HYPERX_QC2_MUTE_LEN	3
+
+struct hyperx_drvdata {
+	struct input_dev *input;
+	bool muted;
+	bool have_state;
+};
+
+static int hyperx_input_configured(struct hid_device *hdev,
+				   struct hid_input *hi)
+{
+	struct hyperx_drvdata *drvdata = hid_get_drvdata(hdev);
+
+	/*
+	 * The device exposes several application collections.  Prefer the
+	 * telephony one, which already advertises KEY_MICMUTE, and fall back
+	 * to the first collection otherwise.
+	 */
+	if (!drvdata->input || test_bit(KEY_MICMUTE, hi->input->keybit)) {
+		drvdata->input = hi->input;
+		input_set_capability(drvdata->input, EV_KEY, KEY_MICMUTE);
+	}
+
+	return 0;
+}
+
+static int hyperx_raw_event(struct hid_device *hdev, struct hid_report *report,
+			    u8 *data, int size)
+{
+	struct hyperx_drvdata *drvdata = hid_get_drvdata(hdev);
+	bool muted;
+
+	if (!(hdev->claimed & HID_CLAIMED_INPUT) || !drvdata->input)
+		return 0;
+
+	if (size < HYPERX_QC2_MUTE_LEN || data[0] != HYPERX_QC2_REPORT_ID ||
+	    data[1] != HYPERX_QC2_EVENT_MUTE)
+		return 0;
+
+	muted = data[2];
+	if (drvdata->have_state && muted == drvdata->muted)
+		return 0;
+
+	drvdata->muted = muted;
+	drvdata->have_state = true;
+
+	/*
+	 * The device reports the resulting absolute state, while KEY_MICMUTE is
+	 * a momentary key that userspace acts on as a toggle.  Emit one
+	 * keypress per state change.
+	 */
+	input_report_key(drvdata->input, KEY_MICMUTE, 1);
+	input_sync(drvdata->input);
+	input_report_key(drvdata->input, KEY_MICMUTE, 0);
+	input_sync(drvdata->input);
+
+	return 0;
+}
+
+static int hyperx_probe(struct hid_device *hdev, const struct hid_device_id *id)
+{
+	struct hyperx_drvdata *drvdata;
+	int ret;
+
+	drvdata = devm_kzalloc(&hdev->dev, sizeof(*drvdata), GFP_KERNEL);
+	if (!drvdata)
+		return -ENOMEM;
+
+	hid_set_drvdata(hdev, drvdata);
+
+	ret = hid_parse(hdev);
+	if (ret)
+		return ret;
+
+	return hid_hw_start(hdev, HID_CONNECT_DEFAULT);
+}
+
+static const struct hid_device_id hyperx_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_HP,
+			 USB_PRODUCT_ID_HP_HYPERX_QUADCAST_2) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, hyperx_devices);
+
+static struct hid_driver hyperx_driver = {
+	.name			= "hyperx",
+	.id_table		= hyperx_devices,
+	.probe			= hyperx_probe,
+	.input_configured	= hyperx_input_configured,
+	.raw_event		= hyperx_raw_event,
+};
+module_hid_driver(hyperx_driver);
+
+MODULE_DESCRIPTION("HID driver for the HyperX QuadCast 2 microphone");
+MODULE_AUTHOR("Benjamin Blume <benjaminblume@posteo.de>");
+MODULE_LICENSE("GPL");