[PATCH] HID: lg-g15: cancel pending work on remove to fix a use-after-free

[Maoyi Xie]

lg_g15_data is allocated with devm and holds a work item. The report
handlers schedule that work straight from device input.
lg_g15_event() and lg_g15_v2_event() do it on the backlight cycle key,
and lg_g510_leds_event() does it too. The worker dereferences the
lg_g15_data back through container_of.

The driver had no remove callback and never cancelled the work. So if a
report scheduled the work and the keyboard was then unplugged, devres
freed lg_g15_data while the work was still pending or running, and the
worker touched freed memory. This is a use-after-free. It is reachable
as a race on device unplug.

Add a remove callback that cancels the work before devres frees the
state. g15->work is only initialized for the models that schedule it
(G15, G15 v2, G510). The G13 and Z-10 leave it zeroed, so guard the
cancel on g15->work.func to avoid cancelling a work that was never set
up. The g15 NULL test mirrors the one already in lg_g15_raw_event().

Fixes: 97b741aba918 ("HID: lg-g15: Add keyboard and LCD backlight control")
Cc: stable@xxxxxxxxxxxxxxx
Suggested-by: Hans de Goede <hansg@xxxxxxxxxx>
Signed-off-by: Maoyi Xie <maoyixie.tju@xxxxxxxxx>
---
 drivers/hid/hid-lg-g15.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/hid/hid-lg-g15.c b/drivers/hid/hid-lg-g15.c
index 1a88bc44ada4..02ef3e2094b4 100644
--- a/drivers/hid/hid-lg-g15.c
+++ b/drivers/hid/hid-lg-g15.c
@@ -1374,11 +1374,27 @@ static const struct hid_device_id lg_g15_devices[] = {
 };
 MODULE_DEVICE_TABLE(hid, lg_g15_devices);
 
+static void lg_g15_remove(struct hid_device *hdev)
+{
+	struct lg_g15_data *g15 = hid_get_drvdata(hdev);
+
+	/*
+	 * g15->work is only initialized for the models that schedule it
+	 * (G15, G15 v2, G510). The G13 and Z-10 leave it zeroed, so only
+	 * cancel it when it was set up.
+	 */
+	if (g15 && g15->work.func)
+		cancel_work_sync(&g15->work);
+
+	hid_hw_stop(hdev);
+}
+
 static struct hid_driver lg_g15_driver = {
 	.name			= "lg-g15",
 	.id_table		= lg_g15_devices,
 	.raw_event		= lg_g15_raw_event,
 	.probe			= lg_g15_probe,
+	.remove			= lg_g15_remove,
 };
 module_hid_driver(lg_g15_driver);
 
-- 
2.34.1