[DO NOT APPLY THIS PATCH] :)
This is the patch I used to simulate each possible failure case
in the probing function.
I can say going it was worth it, as I was originally not gating
ida_free, and the struct would corrupt.

Below are the logs from my last run with this.
I added a space between each iteration, to help reading:

[   76.680204] wiimote 0005:057E:0330.0006: Probing wiimote iteration 1
[   76.680216] __wiimote_probe_cleanup: wdata NULL
[   76.680224] wiimote 0005:057E:0330.0006: probe with driver wiimote failed with error -12

[   81.745168] wiimote 0005:057E:0330.0007: Probing wiimote iteration 2
[   81.745312] wiimote 0005:057E:0330.0007: probe with driver wiimote failed with error -12

[   86.869452] wiimote 0005:057E:0330.0008: Probing wiimote iteration 3
[   86.869935] wiimote 0005:057E:0330.0008: unknown main item tag 0x0
[   86.869983] wiimote 0005:057E:0330.0008: probe with driver wiimote failed with error -12

[   92.001194] wiimote 0005:057E:0330.0009: Probing wiimote iteration 4
[   92.001684] wiimote 0005:057E:0330.0009: unknown main item tag 0x0
[   92.001905] wiimote 0005:057E:0330.0009: hidraw5: BLUETOOTH HID v0.01 Gamepad [Nintendo RVL-CNT-01-TR] on 64:bc:58:9a:b9:28
[   92.002075] __wiimote_probe_cleanup: hid_hw_stop cleanup
[   92.002105] wiimote 0005:057E:0330.0009: probe with driver wiimote failed with error -12

[   97.129059] wiimote 0005:057E:0330.000A: Probing wiimote iteration 5
[   97.129528] wiimote 0005:057E:0330.000A: unknown main item tag 0x0
[   97.129757] wiimote 0005:057E:0330.000A: hidraw5: BLUETOOTH HID v0.01 Gamepad [Nintendo RVL-CNT-01-TR] on 64:bc:58:9a:b9:28
[   97.129774] __wiimote_probe_cleanup: hid_hw_close cleanup
[   97.129934] __wiimote_probe_cleanup: hid_hw_stop cleanup
[   97.129962] wiimote 0005:057E:0330.000A: probe with driver wiimote failed with error -12

[  102.265442] wiimote 0005:057E:0330.000B: Probing wiimote iteration 6
[  102.265925] wiimote 0005:057E:0330.000B: unknown main item tag 0x0
[  102.266521] wiimote 0005:057E:0330.000B: hidraw5: BLUETOOTH HID v0.01 Gamepad [Nintendo RVL-CNT-01-TR] on 64:bc:58:9a:b9:28
[  102.266538] __wiimote_probe_cleanup: hid_hw_close cleanup
[  102.266814] __wiimote_probe_cleanup: hid_hw_stop cleanup
[  102.266844] wiimote 0005:057E:0330.000B: probe with driver wiimote failed with error -12

[  107.405172] wiimote 0005:057E:0330.000C: Probing wiimote iteration 7
[  107.405602] wiimote 0005:057E:0330.000C: unknown main item tag 0x0
[  107.405776] wiimote 0005:057E:0330.000C: hidraw5: BLUETOOTH HID v0.01 Gamepad [Nintendo RVL-CNT-01-TR] on 64:bc:58:9a:b9:28
[  107.405794] __wiimote_probe_cleanup: hid_hw_close cleanup
[  107.405953] __wiimote_probe_cleanup: hid_hw_stop cleanup
[  107.405981] wiimote 0005:057E:0330.000C: probe with driver wiimote failed with error -12

[  112.525411] wiimote 0005:057E:0330.000D: Probing wiimote iteration 8
[  112.525883] wiimote 0005:057E:0330.000D: unknown main item tag 0x0
[  112.526323] wiimote 0005:057E:0330.000D: hidraw5: BLUETOOTH HID v0.01 Gamepad [Nintendo RVL-CNT-01-TR] on 64:bc:58:9a:b9:28
[  112.526362] __wiimote_probe_cleanup: hid_hw_close cleanup
[  112.526511] __wiimote_probe_cleanup: hid_hw_stop cleanup
[  112.526535] wiimote 0005:057E:0330.000D: probe with driver wiimote failed with error -12

[  117.673238] wiimote 0005:057E:0330.000E: Probing wiimote iteration 9
[  117.673700] wiimote 0005:057E:0330.000E: unknown main item tag 0x0
[  117.673885] wiimote 0005:057E:0330.000E: hidraw5: BLUETOOTH HID v0.01 Gamepad [Nintendo RVL-CNT-01-TR] on 64:bc:58:9a:b9:28
[  117.673909] __wiimote_probe_cleanup: ida cleanup
[  117.673929] __wiimote_probe_cleanup: hid_hw_close cleanup
[  117.674081] __wiimote_probe_cleanup: hid_hw_stop cleanup
[  117.674105] wiimote 0005:057E:0330.000E: probe with driver wiimote failed with error -12

[  122.805206] wiimote 0005:057E:0330.000F: Probing wiimote iteration 10
[  122.805669] wiimote 0005:057E:0330.000F: unknown main item tag 0x0
[  122.805895] wiimote 0005:057E:0330.000F: hidraw5: BLUETOOTH HID v0.01 Gamepad [Nintendo RVL-CNT-01-TR] on 64:bc:58:9a:b9:28
[  122.805934] wiimote 0005:057E:0330.000F: New device registered (Wiimote 1)
[  122.805940] __wiimote_probe_cleanup: wdata NULL
[  122.841287] wiimote 0005:057E:0330.000F: detected device: Nintendo Wii Remote Plus (Gen 2) (1)
[  122.841759] input: Nintendo Wii Remote Accelerometer as /devices/virtual/misc/uhid/0005:057E:0330.000F/input/input33
[  122.844724] input: Nintendo Wii Remote IR as /devices/virtual/misc/uhid/0005:057E:0330.000F/input/input34
[  122.845091] input: Nintendo Wii Remote as /devices/virtual/misc/uhid/0005:057E:0330.000F/input/input32
[  122.965128] wiimote 0005:057E:0330.000F: detected extension: Nintendo Wii Motion Plus
[  122.965276] input: Nintendo Wii Remote Motion Plus as /devices/virtual/misc/uhid/0005:057E:0330.000F/input/input35
[  127.877355] wiimote 0005:057E:0330.000F: Device removed

[  130.497046] wiimote 0005:057E:0330.0010: Probing wiimote iteration 11
[  130.497524] wiimote 0005:057E:0330.0010: unknown main item tag 0x0
[  130.497838] wiimote 0005:057E:0330.0010: hidraw5: BLUETOOTH HID v0.01 Gamepad [Nintendo RVL-CNT-01-TR] on 64:bc:58:9a:b9:28
[  130.497869] wiimote 0005:057E:0330.0010: New device registered (Wiimote 1)
[  130.497874] __wiimote_probe_cleanup: wdata NULL
[  130.533040] wiimote 0005:057E:0330.0010: detected device: Nintendo Wii Remote Plus (Gen 2) (1)
[  130.533424] input: Nintendo Wii Remote Accelerometer as /devices/virtual/misc/uhid/0005:057E:0330.0010/input/input37
[  130.533579] input: Nintendo Wii Remote IR as /devices/virtual/misc/uhid/0005:057E:0330.0010/input/input38
[  130.533699] input: Nintendo Wii Remote as /devices/virtual/misc/uhid/0005:057E:0330.0010/input/input36
[  130.641239] wiimote 0005:057E:0330.0010: detected extension: Nintendo Wii Motion Plus
[  130.641385] input: Nintendo Wii Remote Motion Plus as /devices/virtual/misc/uhid/0005:057E:0330.0010/input/input39
[  134.317450] wiimote 0005:057E:0330.0010: Device removed


Signed-off-by: Rafael Passos <redacted>
---
 drivers/hid/hid-wiimote-core.c | 45 ++++++++++++++++++++++++++++++----
 1 file changed, 40 insertions(+), 5 deletions(-)

diff --git a/drivers/hid/hid-wiimote-core.c b/drivers/hid/hid-wiimote-core.c
--- a/drivers/hid/hid-wiimote-core.c
+++ b/drivers/hid/hid-wiimote-core.c

@@ -1779,52 +1779,77 @@ static DEFINE_IDA(wiimote_ida);
 
 static void __wiimote_probe_cleanup(struct wiimote_data *wdata)
 {
-	if (!wdata)
+	if (!wdata) {
+		printk(KERN_INFO "%s: wdata NULL\n", __func__);
 		return;
+	}
 
-	if (wdata->player_id)
+	if (wdata->player_id){
+		printk(KERN_INFO "%s: ida cleanup\n", __func__);
 		ida_free(&wiimote_ida, wdata->player_id);
+	}
 
 	// safe, debugfs checks IS_ERR_OR_NULL
 	wiidebug_deinit(wdata);
 	// safe, checks dev for NULL
 	device_remove_file(&wdata->hdev->dev, &dev_attr_devtype);
 	device_remove_file(&wdata->hdev->dev, &dev_attr_extension);
-	if (wdata->probe_state & WIIMOTE_PROBE_HW_OPENED)
+	if (wdata->probe_state & WIIMOTE_PROBE_HW_OPENED){
+		printk(KERN_INFO "%s: hid_hw_close cleanup\n", __func__);
 		hid_hw_close(wdata->hdev);
-	if (wdata->probe_state & WIIMOTE_PROBE_HW_STARTED)
+	}
+	if (wdata->probe_state & WIIMOTE_PROBE_HW_STARTED){
 		hid_hw_stop(wdata->hdev);
+		printk(KERN_INFO "%s: hid_hw_stop cleanup\n", __func__);
+	}
 	kfree(wdata);
 }
 
 DEFINE_FREE(wiimote_probe_cleanup, struct wiimote_data *,
 	__wiimote_probe_cleanup(_T))
 
+static int debug_connect_iterate = 0;
+
 static int wiimote_hid_probe(struct hid_device *hdev,
 				const struct hid_device_id *id)
 {
 	int ret;
+	debug_connect_iterate++;
+
+	hid_info(hdev, "Probing wiimote iteration %d\n", debug_connect_iterate);
 
 	hdev->quirks |= HID_QUIRK_NO_INIT_REPORTS;
 
-	struct wiimote_data *wdata __free(wiimote_probe_cleanup) = wiimote_create(hdev);
+	struct wiimote_data *wdata __free(wiimote_probe_cleanup) = NULL;
+	if (debug_connect_iterate == 1)
+		return -ENOMEM;
+
+        wdata = wiimote_create(hdev);
 	if (!wdata) {
 		hid_err(hdev, "Can't alloc device\n");
 		return -ENOMEM;
 	}
 
+	if (debug_connect_iterate == 2)
+		return -ENOMEM;
+
 	ret = hid_parse(hdev);
 	if (ret) {
 		hid_err(hdev, "HID parse failed\n");
 		return ret;
 	}
 
+	if (debug_connect_iterate == 3)
+		return -ENOMEM;
+
 	ret = hid_hw_start(hdev, HID_CONNECT_HIDRAW);
 	if (ret) {
 		hid_err(hdev, "HW start failed\n");
 		return ret;
 	}
 	wdata->probe_state |= WIIMOTE_PROBE_HW_STARTED;
+	if (debug_connect_iterate == 4)
+		return -ENOMEM;
 
 	ret = hid_hw_open(hdev);
 	if (ret) {

@@ -1832,22 +1857,30 @@ static int wiimote_hid_probe(struct hid_device *hdev,
 		return ret;
 	}
 	wdata->probe_state |= WIIMOTE_PROBE_HW_OPENED;
+	if (debug_connect_iterate == 5)
+		return -ENOMEM;
 
 	ret = device_create_file(&hdev->dev, &dev_attr_extension);
 	if (ret) {
 		hid_err(hdev, "cannot create sysfs attribute\n");
 		return ret;
 	}
+	if (debug_connect_iterate == 6)
+		return -ENOMEM;
 
 	ret = device_create_file(&hdev->dev, &dev_attr_devtype);
 	if (ret) {
 		hid_err(hdev, "cannot create sysfs attribute\n");
 		return ret;
 	}
+	if (debug_connect_iterate == 7)
+		return -ENOMEM;
 
 	ret = wiidebug_init(wdata);
 	if (ret)
 		return ret;
+	if (debug_connect_iterate == 8)
+		return -ENOMEM;
 
 	int player_id = ida_alloc_min(&wiimote_ida, 1, GFP_KERNEL);
 	if (player_id < 1) {

@@ -1856,6 +1889,8 @@ static int wiimote_hid_probe(struct hid_device *hdev,
 		return ret;
 	}
 	wdata->player_id = player_id;
+	if (debug_connect_iterate == 9)
+		return -ENOMEM;
 
 
 	hid_info(hdev, "New device registered (Wiimote %d)\n", player_id);

-- 
2.53.0