[PATCH v2 1/7] HID: sensor: hub: Synchronize callback removal with raw events

[Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>]

Raw-event processing holds pdata->lock across callback lookup and
invocation, and takes dyn_callback_lock during lookup. Removal must
prevent both active callbacks and future lookups before client state can
be released.

Take pdata->lock before dyn_callback_lock, matching raw-event order,
and unlink the callback while holding both locks. This ensures active
raw-event callbacks have finished and prevents future lookups.

Fixes: 401ca24fb34a ("HID: sensors: introduce sensor framework")
Reported-by: Семён Марьясин <simeon@maryasin.name>
Closes: https://lore.kernel.org/all/CAM2dg7ewfVJSP4rFyhkCB1Rmd1+X56sAg=eUdbPthG2xrLqwQQ@mail.gmail.com/
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
---
 drivers/hid/hid-sensor-hub.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/hid/hid-sensor-hub.c b/drivers/hid/hid-sensor-hub.c
index 6470a290ebfc..0c4884c5821f 100644
--- a/drivers/hid/hid-sensor-hub.c
+++ b/drivers/hid/hid-sensor-hub.c
@@ -173,7 +173,9 @@ int sensor_hub_remove_callback(struct hid_sensor_hub_device *hsdev,
 	struct sensor_hub_data *pdata = hid_get_drvdata(hsdev->hdev);
 	unsigned long flags;
 
-	spin_lock_irqsave(&pdata->dyn_callback_lock, flags);
+	/* Serialize callback removal with raw-event callback execution. */
+	spin_lock_irqsave(&pdata->lock, flags);
+	spin_lock(&pdata->dyn_callback_lock);
 	list_for_each_entry(callback, &pdata->dyn_callback_list, list)
 		if (callback->usage_id == usage_id &&
 						callback->hsdev == hsdev) {
@@ -181,7 +183,8 @@ int sensor_hub_remove_callback(struct hid_sensor_hub_device *hsdev,
 			kfree(callback);
 			break;
 		}
-	spin_unlock_irqrestore(&pdata->dyn_callback_lock, flags);
+	spin_unlock(&pdata->dyn_callback_lock);
+	spin_unlock_irqrestore(&pdata->lock, flags);
 
 	return 0;
 }
-- 
2.56.0