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, 147 insertions, 0 deletions

diff --git a/drivers/hid/hid-lg3ff.c b/drivers/hid/hid-lg3ff.c
new file mode 100644
index 000000000..109735b89
--- /dev/null
+++ b/drivers/hid/hid-lg3ff.c
@@ -0,0 +1,147 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Force feedback support for Logitech Flight System G940
+ *
+ *  Copyright (c) 2009 Gary Stein <LordCnidarian@gmail.com>
+ */
+
+/*
+ */
+
+
+#include <linux/input.h>
+#include <linux/hid.h>
+
+#include "hid-lg.h"
+
+/*
+ * G940 Theory of Operation (from experimentation)
+ *
+ * There are 63 fields (only 3 of them currently used)
+ * 0 - seems to be command field
+ * 1 - 30 deal with the x axis
+ * 31 -60 deal with the y axis
+ *
+ * Field 1 is x axis constant force
+ * Field 31 is y axis constant force
+ *
+ * other interesting fields 1,2,3,4 on x axis
+ * (same for 31,32,33,34 on y axis)
+ *
+ * 0 0 127 127 makes the joystick autocenter hard
+ *
+ * 127 0 127 127 makes the joystick loose on the right,
+ * but stops all movemnt left
+ *
+ * -127 0 -127 -127 makes the joystick loose on the left,
+ * but stops all movement right
+ *
+ * 0 0 -127 -127 makes the joystick rattle very hard
+ *
+ * I'm sure these are effects that I don't know enough about them
+ */
+
+static int hid_lg3ff_play(struct input_dev *dev, void *data,
+			 struct ff_effect *effect)
+{
+	struct hid_device *hid = input_get_drvdata(dev);
+	struct list_head *report_list = &hid->report_enum[HID_OUTPUT_REPORT].report_list;
+	struct hid_report *report = list_entry(report_list->next, struct hid_report, list);
+	int x, y;
+
+/*
+ * Available values in the field should always be 63, but we only use up to
+ * 35. Instead, clear the entire area, however big it is.
+ */
+	memset(report->field[0]->value, 0,
+	       sizeof(__s32) * report->field[0]->report_count);
+
+	switch (effect->type) {
+	case FF_CONSTANT:
+/*
+ * Already clamped in ff_memless
+ * 0 is center (different then other logitech)
+ */
+		x = effect->u.ramp.start_level;
+		y = effect->u.ramp.end_level;
+
+		/* send command byte */
+		report->field[0]->value[0] = 0x51;
+
+/*
+ * Sign backwards from other Force3d pro
+ * which get recast here in two's complement 8 bits
+ */
+		report->field[0]->value[1] = (unsigned char)(-x);
+		report->field[0]->value[31] = (unsigned char)(-y);
+
+		hid_hw_request(hid, report, HID_REQ_SET_REPORT);
+		break;
+	}
+	return 0;
+}
+static void hid_lg3ff_set_autocenter(struct input_dev *dev, u16 magnitude)
+{
+	struct hid_device *hid = input_get_drvdata(dev);
+	struct list_head *report_list = &hid->report_enum[HID_OUTPUT_REPORT].report_list;
+	struct hid_report *report = list_entry(report_list->next, struct hid_report, list);
+
+/*
+ * Auto Centering probed from device
+ * NOTE: deadman's switch on G940 must be covered
+ * for effects to work
+ */
+	report->field[0]->value[0] = 0x51;
+	report->field[0]->value[1] = 0x00;
+	report->field[0]->value[2] = 0x00;
+	report->field[0]->value[3] = 0x7F;
+	report->field[0]->value[4] = 0x7F;
+	report->field[0]->value[31] = 0x00;
+	report->field[0]->value[32] = 0x00;
+	report->field[0]->value[33] = 0x7F;
+	report->field[0]->value[34] = 0x7F;
+
+	hid_hw_request(hid, report, HID_REQ_SET_REPORT);
+}
+
+
+static const signed short ff3_joystick_ac[] = {
+	FF_CONSTANT,
+	FF_AUTOCENTER,
+	-1
+};
+
+int lg3ff_init(struct hid_device *hid)
+{
+	struct hid_input *hidinput;
+	struct input_dev *dev;
+	const signed short *ff_bits = ff3_joystick_ac;
+	int error;
+	int i;
+
+	if (list_empty(&hid->inputs)) {
+		hid_err(hid, "no inputs found\n");
+		return -ENODEV;
+	}
+	hidinput = list_entry(hid->inputs.next, struct hid_input, list);
+	dev = hidinput->input;
+
+	/* Check that the report looks ok */
+	if (!hid_validate_values(hid, HID_OUTPUT_REPORT, 0, 0, 35))
+		return -ENODEV;
+
+	/* Assume single fixed device G940 */
+	for (i = 0; ff_bits[i] >= 0; i++)
+		set_bit(ff_bits[i], dev->ffbit);
+
+	error = input_ff_create_memless(dev, NULL, hid_lg3ff_play);
+	if (error)
+		return error;
+
+	if (test_bit(FF_AUTOCENTER, dev->ffbit))
+		dev->ff->set_autocenter = hid_lg3ff_set_autocenter;
+
+	hid_info(hid, "Force feedback for Logitech Flight System G940 by Gary Stein <LordCnidarian@gmail.com>\n");
+	return 0;
+}
+