[PATCH] media: mediatek: vcodec: unregister VPU watchdog handler

[Guangshuo Li]

mtk_vcodec_fw_vpu_init() registers a VPU watchdog reset handler and
passes the vcodec device as the private data.

The handler is stored in the VPU device and can outlive the vcodec
device. If firmware initialization fails after the handler has been
registered, or if the vcodec device is later removed, the VPU watchdog
table can keep a pointer to a vcodec device that is about to be released.
A later VPU watchdog reset can then call the reset handler with a stale
pointer and dereference freed memory while walking the vcodec context
list.

Add a VPU watchdog unregister helper and clear the vcodec watchdog
handler from both the firmware initialization failure path and the VPU
firmware release path before dropping the VPU device reference.

Fixes: 01abf5fbb081 ("media: mediatek: vcodec: separate struct 'mtk_vcodec_ctx'")
Signed-off-by: Guangshuo Li <lgs201920130244 at gmail.com>
---
 .../mediatek/vcodec/common/mtk_vcodec_fw_vpu.c    |  4 ++++
 drivers/media/platform/mediatek/vpu/mtk_vpu.c     | 15 +++++++++++++++
 drivers/media/platform/mediatek/vpu/mtk_vpu.h     |  2 ++
 3 files changed, 21 insertions(+)

diff --git a/drivers/media/platform/mediatek/vcodec/common/mtk_vcodec_fw_vpu.c b/drivers/media/platform/mediatek/vcodec/common/mtk_vcodec_fw_vpu.c
index 3632037f78f5..c79a78c371ea 100644
--- a/drivers/media/platform/mediatek/vcodec/common/mtk_vcodec_fw_vpu.c
+++ b/drivers/media/platform/mediatek/vcodec/common/mtk_vcodec_fw_vpu.c
@@ -40,6 +40,9 @@ static int mtk_vcodec_vpu_ipi_send(struct mtk_vcodec_fw *fw, int id, void *buf,
 
 static void mtk_vcodec_vpu_release(struct mtk_vcodec_fw *fw)
 {
+	vpu_wdt_unreg_handler(fw->pdev,
+			      fw->fw_use == ENCODER ? VPU_RST_ENC :
+				       VPU_RST_DEC);
 	put_device(&fw->pdev->dev);
 }
 
@@ -120,6 +123,7 @@ struct mtk_vcodec_fw *mtk_vcodec_fw_vpu_init(void *priv, enum mtk_vcodec_fw_use
 
 	fw = devm_kzalloc(&plat_dev->dev, sizeof(*fw), GFP_KERNEL);
 	if (!fw) {
+		vpu_wdt_unreg_handler(fw_pdev, rst_id);
 		put_device(&fw_pdev->dev);
 		return ERR_PTR(-ENOMEM);
 	}
diff --git a/drivers/media/platform/mediatek/vpu/mtk_vpu.c b/drivers/media/platform/mediatek/vpu/mtk_vpu.c
index 8d8319f0cd22..f59f45fecc75 100644
--- a/drivers/media/platform/mediatek/vpu/mtk_vpu.c
+++ b/drivers/media/platform/mediatek/vpu/mtk_vpu.c
@@ -437,6 +437,21 @@ int vpu_wdt_reg_handler(struct platform_device *pdev,
 }
 EXPORT_SYMBOL_GPL(vpu_wdt_reg_handler);
 
++void vpu_wdt_unreg_handler(struct platform_device *pdev, enum rst_id id)
+{
+	struct mtk_vpu *vpu = platform_get_drvdata(pdev);
+
+	if (!vpu || id >= VPU_RST_MAX)
+		return;
+
+	mutex_lock(&vpu->vpu_mutex);
+	vpu->wdt.handler[id].reset_func = NULL;
+	vpu->wdt.handler[id].priv = NULL;
+	mutex_unlock(&vpu->vpu_mutex);
+}
+EXPORT_SYMBOL_GPL(vpu_wdt_unreg_handler);
+
+
 unsigned int vpu_get_vdec_hw_capa(struct platform_device *pdev)
 {
 	struct mtk_vpu *vpu = platform_get_drvdata(pdev);
diff --git a/drivers/media/platform/mediatek/vpu/mtk_vpu.h b/drivers/media/platform/mediatek/vpu/mtk_vpu.h
index 3951547e9ec5..2ccb481a04cf 100644
--- a/drivers/media/platform/mediatek/vpu/mtk_vpu.h
+++ b/drivers/media/platform/mediatek/vpu/mtk_vpu.h
@@ -141,6 +141,8 @@ int vpu_wdt_reg_handler(struct platform_device *pdev,
 			void vpu_wdt_reset_func(void *priv),
 			void *priv, enum rst_id id);
 
+void vpu_wdt_unreg_handler(struct platform_device *pdev, enum rst_id id);
+
 /**
  * vpu_get_vdec_hw_capa - get video decoder hardware capability
  *
-- 
2.43.0