[PATCH v3,2/2] media: mediatek: vcodec: adding lock to protect encoder context list

[Sebastian Fricke]

Hey Yunfei,

On 22.02.2024 17:26, Yunfei Dong wrote:
>The ctx_list will be deleted when scp getting unexpected behavior, then the
>ctx_list->next will be NULL, the kernel driver maybe access NULL pointer in
>function vpu_enc_ipi_handler when going through each context, then reboot.
>
>Need to add lock to protect the ctx_list to make sure the ctx_list->next isn't
>NULL pointer.

Can we reword this slightly to make it grammatically correct?

My suggestion:
```
Add a lock for the ctx_list, to avoid accessing a NULL pointer within
the `vpu_enc_ipi_handler` function, when the ctx_list has been deleted
due to an unexpected behavior on the SCP IP block.
```

Greetings,
Sebastian

>
>Fixes: 1972e32431ed ("media: mediatek: vcodec: Fix possible invalid memory access for encoder")
>Signed-off-by: Yunfei Dong <yunfei.dong at mediatek.com>
>---
> .../platform/mediatek/vcodec/common/mtk_vcodec_fw_vpu.c      | 4 ++--
> .../platform/mediatek/vcodec/encoder/mtk_vcodec_enc_drv.c    | 5 +++++
> .../platform/mediatek/vcodec/encoder/mtk_vcodec_enc_drv.h    | 2 ++
> drivers/media/platform/mediatek/vcodec/encoder/venc_vpu_if.c | 2 ++
> 4 files changed, 11 insertions(+), 2 deletions(-)
>
>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 9a11a2c248045..8d578b6902148 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
>@@ -73,12 +73,12 @@ static void mtk_vcodec_vpu_reset_enc_handler(void *priv)
>
> 	dev_err(&dev->plat_dev->dev, "Watchdog timeout!!");
>
>-	mutex_lock(&dev->dev_mutex);
>+	mutex_lock(&dev->dev_ctx_lock);
> 	list_for_each_entry(ctx, &dev->ctx_list, list) {
> 		ctx->state = MTK_STATE_ABORT;
> 		mtk_v4l2_vdec_dbg(0, ctx, "[%d] Change to state MTK_STATE_ABORT", ctx->id);
> 	}
>-	mutex_unlock(&dev->dev_mutex);
>+	mutex_unlock(&dev->dev_ctx_lock);
> }
>
> static const struct mtk_vcodec_fw_ops mtk_vcodec_vpu_msg = {
>diff --git a/drivers/media/platform/mediatek/vcodec/encoder/mtk_vcodec_enc_drv.c b/drivers/media/platform/mediatek/vcodec/encoder/mtk_vcodec_enc_drv.c
>index 5db2bf3db4c54..29524cd59ce8b 100644
>--- a/drivers/media/platform/mediatek/vcodec/encoder/mtk_vcodec_enc_drv.c
>+++ b/drivers/media/platform/mediatek/vcodec/encoder/mtk_vcodec_enc_drv.c
>@@ -177,7 +177,9 @@ static int fops_vcodec_open(struct file *file)
> 	mtk_v4l2_venc_dbg(2, ctx, "Create instance [%d]@%p m2m_ctx=%p ",
> 			  ctx->id, ctx, ctx->m2m_ctx);
>
>+	mutex_lock(&dev->dev_ctx_lock);
> 	list_add(&ctx->list, &dev->ctx_list);
>+	mutex_unlock(&dev->dev_ctx_lock);
>
> 	mutex_unlock(&dev->dev_mutex);
> 	mtk_v4l2_venc_dbg(0, ctx, "%s encoder [%d]", dev_name(&dev->plat_dev->dev),
>@@ -212,7 +214,9 @@ static int fops_vcodec_release(struct file *file)
> 	v4l2_fh_exit(&ctx->fh);
> 	v4l2_ctrl_handler_free(&ctx->ctrl_hdl);
>
>+	mutex_lock(&dev->dev_ctx_lock);
> 	list_del_init(&ctx->list);
>+	mutex_unlock(&dev->dev_ctx_lock);
> 	kfree(ctx);
> 	mutex_unlock(&dev->dev_mutex);
> 	return 0;
>@@ -294,6 +298,7 @@ static int mtk_vcodec_probe(struct platform_device *pdev)
>
> 	mutex_init(&dev->enc_mutex);
> 	mutex_init(&dev->dev_mutex);
>+	mutex_init(&dev->dev_ctx_lock);
> 	spin_lock_init(&dev->irqlock);
>
> 	snprintf(dev->v4l2_dev.name, sizeof(dev->v4l2_dev.name), "%s",
>diff --git a/drivers/media/platform/mediatek/vcodec/encoder/mtk_vcodec_enc_drv.h b/drivers/media/platform/mediatek/vcodec/encoder/mtk_vcodec_enc_drv.h
>index a042f607ed8d1..0bd85d0fb379a 100644
>--- a/drivers/media/platform/mediatek/vcodec/encoder/mtk_vcodec_enc_drv.h
>+++ b/drivers/media/platform/mediatek/vcodec/encoder/mtk_vcodec_enc_drv.h
>@@ -178,6 +178,7 @@ struct mtk_vcodec_enc_ctx {
>  *
>  * @enc_mutex: encoder hardware lock.
>  * @dev_mutex: video_device lock
>+ * @dev_ctx_lock: the lock of context list
>  * @encode_workqueue: encode work queue
>  *
>  * @enc_irq: h264 encoder irq resource
>@@ -205,6 +206,7 @@ struct mtk_vcodec_enc_dev {
> 	/* encoder hardware mutex lock */
> 	struct mutex enc_mutex;
> 	struct mutex dev_mutex;
>+	struct mutex dev_ctx_lock;
> 	struct workqueue_struct *encode_workqueue;
>
> 	int enc_irq;
>diff --git a/drivers/media/platform/mediatek/vcodec/encoder/venc_vpu_if.c b/drivers/media/platform/mediatek/vcodec/encoder/venc_vpu_if.c
>index 84ad1cc6ad171..51bb7ee141b9e 100644
>--- a/drivers/media/platform/mediatek/vcodec/encoder/venc_vpu_if.c
>+++ b/drivers/media/platform/mediatek/vcodec/encoder/venc_vpu_if.c
>@@ -47,12 +47,14 @@ static bool vpu_enc_check_ap_inst(struct mtk_vcodec_enc_dev *enc_dev, struct ven
> 	struct mtk_vcodec_enc_ctx *ctx;
> 	int ret = false;
>
>+	mutex_lock(&enc_dev->dev_ctx_lock);
> 	list_for_each_entry(ctx, &enc_dev->ctx_list, list) {
> 		if (!IS_ERR_OR_NULL(ctx) && ctx->vpu_inst == vpu) {
> 			ret = true;
> 			break;
> 		}
> 	}
>+	mutex_unlock(&enc_dev->dev_ctx_lock);
>
> 	return ret;
> }
>-- 
>2.18.0
>
>