[PATCH] media: mgb4: cancel err_work on teardown to avoid use-after-free

[hyunjungg <hj351016@gmail.com>]

From: Hyunjung Ko <hj351016@gmail.com>

The err IRQ handler (err_handler) schedules vindev->err_work
(signal_change), which dereferences vindev (vindev->mgbdev, vindev->vdev,
vindev->queue). mgb4_vin_free() disables and frees the err IRQ, so no new
err_work is scheduled, but it never cancels an err_work that was already
queued by the last interrupt before kfree(vindev). As err_work runs on
the system workqueue with no timing bound, it can execute after vindev is
freed, dereferencing freed memory -- a use-after-free.

Cancel err_work after the interrupts are freed (so it cannot be
re-queued) and before vindev is freed, mirroring the existing
cancel_work_sync(&vindev->dma_work) in stop_streaming().

Fixes: 0ab13674a9bd ("media: pci: mgb4: Added Digiteq Automotive MGB4 driver")
Cc: stable@vger.kernel.org
Signed-off-by: Hyunjung Ko <hj351016@gmail.com>
---
 drivers/media/pci/mgb4/mgb4_vin.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/media/pci/mgb4/mgb4_vin.c b/drivers/media/pci/mgb4/mgb4_vin.c
index b247854..64b7a9b 100644
--- a/drivers/media/pci/mgb4/mgb4_vin.c
+++ b/drivers/media/pci/mgb4/mgb4_vin.c
@@ -1068,6 +1068,8 @@ void mgb4_vin_free(struct mgb4_vin_dev *vindev)
 	free_irq(vin_irq, vindev);
 	free_irq(err_irq, vindev);
 
+	cancel_work_sync(&vindev->err_work);
+
 	device_remove_groups(&vindev->vdev.dev, module_groups(vindev->mgbdev));
 
 	mgb4_i2c_free(&vindev->deser);
-- 
2.43.0