HID: hid-input: Fix accessing freed memory during device disconnect

During unbinding the driver was dereferencing a pointer to memory
already freed by power_supply_unregister().

Driver was freeing its internal description of battery through pointers
stored in power_supply structure. However, because the core owns the
power supply instance, after calling power_supply_unregister() this
memory is freed and the driver cannot access these members.

Fix this by storing the pointer to internal description of battery in a
local variable before calling power_supply_unregister(), so the pointer
remains valid.

Signed-off-by: Krzysztof Kozlowski <[email protected]>
Reported-by: H.J. Lu <[email protected]>
Fixes: 297d716 ("power_supply: Change ownership from driver to core")
Cc: <[email protected]>
Reviewed-by: Dmitry Torokhov <[email protected]>
Signed-off-by: Jiri Kosina <[email protected]>

Author: krzk

drivers/hid/hid-input.c

@@ -462,12 +462,15 @@ static bool hidinput_setup_battery(struct hid_device *dev, unsigned report_type,
 
 static void hidinput_cleanup_battery(struct hid_device *dev)
 {
+	const struct power_supply_desc *psy_desc;
+
 	if (!dev->battery)
 		return;
 
+	psy_desc = dev->battery->desc;
 	power_supply_unregister(dev->battery);
-	kfree(dev->battery->desc->name);
-	kfree(dev->battery->desc);
+	kfree(psy_desc->name);
+	kfree(psy_desc);
 	dev->battery = NULL;
 }
 #else  /* !CONFIG_HID_BATTERY_STRENGTH */