[PATCH v2 2/3] iio: temperature: hid-sensor-temperature: Use per-instance callbacks

[Christopher Hoover <ch@murgatroid.com>]

hid-sensor-temperature keeps a single static struct
hid_sensor_hub_callbacks for all instances and overwrites its pdev in
every probe.  With two temperature sensors, input reports for one are
delivered with the other's platform device; once that device is
removed, platform_get_drvdata() returns NULL and
temperature_capture_sample() dereferences it:

  BUG: kernel NULL pointer dereference, address: 00000000000003a8
  RIP: 0010:temperature_capture_sample+0xd/0x50 [hid_sensor_temperature]

The oops happens in sensor_hub_raw_event() with the hub's spinlock
held, so the hub's removal then hangs.  It reproduces with two uhid
devices that each declare a temperature sensor, one destroyed while
the other still sends input reports.

Keep the callbacks in struct temperature_state, as the other HID
sensor drivers (accel, gyro, als, ...) do.

Fixes: 59d0f2da3569 ("iio: hid: Add temperature sensor support")
Cc: stable@vger.kernel.org
Signed-off-by: Christopher Hoover <ch@murgatroid.com>
---
 drivers/iio/temperature/hid-sensor-temperature.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/drivers/iio/temperature/hid-sensor-temperature.c b/drivers/iio/temperature/hid-sensor-temperature.c
index 5e3262e461f4..35b8643305b9 100644
--- a/drivers/iio/temperature/hid-sensor-temperature.c
+++ b/drivers/iio/temperature/hid-sensor-temperature.c
@@ -14,6 +14,7 @@
 
 struct temperature_state {
 	struct hid_sensor_common common_attributes;
+	struct hid_sensor_hub_callbacks callbacks;
 	struct hid_sensor_hub_attribute_info temperature_attr;
 	struct {
 		s32 temperature_data;
@@ -181,11 +182,6 @@ static int temperature_parse_report(struct platform_device *pdev,
 	return ret;
 }
 
-static struct hid_sensor_hub_callbacks temperature_callbacks = {
-	.send_event = &temperature_proc_event,
-	.capture_sample = &temperature_capture_sample,
-};
-
 /* Function to initialize the processing for usage id */
 static int hid_temperature_probe(struct platform_device *pdev)
 {
@@ -237,9 +233,11 @@ static int hid_temperature_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, indio_dev);
 
-	temperature_callbacks.pdev = pdev;
+	temp_st->callbacks.send_event = temperature_proc_event;
+	temp_st->callbacks.capture_sample = temperature_capture_sample;
+	temp_st->callbacks.pdev = pdev;
 	ret = sensor_hub_register_callback(hsdev, HID_USAGE_SENSOR_TEMPERATURE,
-					   &temperature_callbacks);
+					   &temp_st->callbacks);
 	if (ret)
 		goto error_remove_trigger;
 
-- 
2.43.0