[PATCH v2 3/3] media: mtk-mdp: unregister VPU watchdog handler

[Guangshuo Li]

mtk_mdp_probe() registers the MDP reset handler with the VPU watchdog
code and passes the MDP device as the private data.

The handler is stored in the VPU device and can outlive the MDP probe or
remove path. If probe fails after the handler has been registered, or if
the MDP device is removed, the watchdog table can retain a pointer to an
MDP object that is about to be released. A later VPU watchdog reset can
then call mtk_mdp_reset_handler() with a stale pointer and dereference
freed memory while queuing the MDP watchdog work.

Unregister the watchdog handler in the probe error path and in the
remove path before dropping the VPU device reference.

Fixes: ee18fc7b0b95 ("media: mtk-mdp: handle vpu_wdt_reg_handler() errors during probe")
Reviewed-by: Nicolas Dufresne <nicolas.dufresne at collabora.com>
Signed-off-by: Guangshuo Li <lgs201920130244 at gmail.com>
---
 drivers/media/platform/mediatek/mdp/mtk_mdp_core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/media/platform/mediatek/mdp/mtk_mdp_core.c b/drivers/media/platform/mediatek/mdp/mtk_mdp_core.c
index 8432833814f3..5ccb7aa925d9 100644
--- a/drivers/media/platform/mediatek/mdp/mtk_mdp_core.c
+++ b/drivers/media/platform/mediatek/mdp/mtk_mdp_core.c
@@ -221,6 +221,7 @@ static int mtk_mdp_probe(struct platform_device *pdev)
 	return 0;
 
 err_reg_handler:
+	vpu_wdt_unreg_handler(mdp->vpu_dev, VPU_RST_MDP);
 	platform_device_put(mdp->vpu_dev);
 
 err_vpu_get_dev:
@@ -254,6 +255,7 @@ static void mtk_mdp_remove(struct platform_device *pdev)
 
 	pm_runtime_disable(&pdev->dev);
 	vb2_dma_contig_clear_max_seg_size(&pdev->dev);
+	vpu_wdt_unreg_handler(mdp->vpu_dev, VPU_RST_MDP);
 	platform_device_put(mdp->vpu_dev);
 	mtk_mdp_unregister_m2m_device(mdp);
 	v4l2_device_unregister(&mdp->v4l2_dev);
-- 
2.43.0