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

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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@xxxxxxxxxxxx>
---
.../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






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