[PATCH v2] dmaegine: virt-dma : Fix multi-user with vchan

[Frank Li]

On Thu, Jun 20, 2024 at 10:53:53AM +0800, Jie Hai wrote:
> List desc_allocated was introduced for the case of a transfer
> submitted multiple times. But elegating descriptors on the list
> causes other problems.
> 
> For example, in the multi-thread scenario, which tasks are
> continuously created and submitted by each thread. If one of
> the threads calls dmaengine_terminate_all, for dirvers using
> vchan_get_all_descriptors, all descriptors will be freed. If
> there's another thread submitting a transfer A by
> vchan_tx_submit, the following results may be generated:
> 1. desc A is freeing -> visit wrong address of node prep/next.
> 2. desc A is freed -> visit invalid address of A.
> 
> In the above case, calltrace is generated and the system is
> suspended. This can be tested by dmatest.

What's test steps to reproduce this problem?

Frank
> 
> This patch removes desc_allocated from vchan_get_all_descriptors,
> and add new function 'vchan_get_all_allocated_descs' to get all
> descriptors ever allocated.
> 
> And apply vchan_get_all_allocated_descs to free chan resource and
> vchan_get_all_descriptors to terminate all transfers, respectively.
> This avoids freeing up descriptors in use by other threads.
> 
> Signed-off-by: Jie Hai <haijie1 at huawei.com>
> ---
>  drivers/dma/fsl-dpaa2-qdma/dpaa2-qdma.c |  2 +-
>  drivers/dma/fsl-edma-common.c           |  2 +-
>  drivers/dma/fsl-qdma.c                  |  2 +-
>  drivers/dma/sf-pdma/sf-pdma.c           |  2 +-
>  drivers/dma/virt-dma.h                  | 20 ++++++++++++++++++--
>  5 files changed, 22 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/dma/fsl-dpaa2-qdma/dpaa2-qdma.c b/drivers/dma/fsl-dpaa2-qdma/dpaa2-qdma.c
> index 36384d019263..efdecf15e1b3 100644
> --- a/drivers/dma/fsl-dpaa2-qdma/dpaa2-qdma.c
> +++ b/drivers/dma/fsl-dpaa2-qdma/dpaa2-qdma.c
> @@ -71,7 +71,7 @@ static void dpaa2_qdma_free_chan_resources(struct dma_chan *chan)
>  	LIST_HEAD(head);
>  
>  	spin_lock_irqsave(&dpaa2_chan->vchan.lock, flags);
> -	vchan_get_all_descriptors(&dpaa2_chan->vchan, &head);
> +	vchan_get_all_allocated_descs(&dpaa2_chan->vchan, &head);
>  	spin_unlock_irqrestore(&dpaa2_chan->vchan.lock, flags);
>  
>  	vchan_dma_desc_free_list(&dpaa2_chan->vchan, &head);
> diff --git a/drivers/dma/fsl-edma-common.c b/drivers/dma/fsl-edma-common.c
> index 3af430787315..1e0ad87eb7fa 100644
> --- a/drivers/dma/fsl-edma-common.c
> +++ b/drivers/dma/fsl-edma-common.c
> @@ -828,7 +828,7 @@ void fsl_edma_free_chan_resources(struct dma_chan *chan)
>  	if (edma->drvdata->dmamuxs)
>  		fsl_edma_chan_mux(fsl_chan, 0, false);
>  	fsl_chan->edesc = NULL;
> -	vchan_get_all_descriptors(&fsl_chan->vchan, &head);
> +	vchan_get_all_allocated_descs(&fsl_chan->vchan, &head);
>  	fsl_edma_unprep_slave_dma(fsl_chan);
>  	spin_unlock_irqrestore(&fsl_chan->vchan.lock, flags);
>  
> diff --git a/drivers/dma/fsl-qdma.c b/drivers/dma/fsl-qdma.c
> index 5005e138fc23..7af428db404e 100644
> --- a/drivers/dma/fsl-qdma.c
> +++ b/drivers/dma/fsl-qdma.c
> @@ -316,7 +316,7 @@ static void fsl_qdma_free_chan_resources(struct dma_chan *chan)
>  	LIST_HEAD(head);
>  
>  	spin_lock_irqsave(&fsl_chan->vchan.lock, flags);
> -	vchan_get_all_descriptors(&fsl_chan->vchan, &head);
> +	vchan_get_all_allocated_descs(&fsl_chan->vchan, &head);
>  	spin_unlock_irqrestore(&fsl_chan->vchan.lock, flags);
>  
>  	vchan_dma_desc_free_list(&fsl_chan->vchan, &head);
> diff --git a/drivers/dma/sf-pdma/sf-pdma.c b/drivers/dma/sf-pdma/sf-pdma.c
> index 428473611115..4dc8a8c8ad80 100644
> --- a/drivers/dma/sf-pdma/sf-pdma.c
> +++ b/drivers/dma/sf-pdma/sf-pdma.c
> @@ -147,7 +147,7 @@ static void sf_pdma_free_chan_resources(struct dma_chan *dchan)
>  	sf_pdma_disable_request(chan);
>  	kfree(chan->desc);
>  	chan->desc = NULL;
> -	vchan_get_all_descriptors(&chan->vchan, &head);
> +	vchan_get_all_allocated_descs(&chan->vchan, &head);
>  	sf_pdma_disclaim_chan(chan);
>  	spin_unlock_irqrestore(&chan->vchan.lock, flags);
>  	vchan_dma_desc_free_list(&chan->vchan, &head);
> diff --git a/drivers/dma/virt-dma.h b/drivers/dma/virt-dma.h
> index 59d9eabc8b67..4492641b79f6 100644
> --- a/drivers/dma/virt-dma.h
> +++ b/drivers/dma/virt-dma.h
> @@ -187,13 +187,29 @@ static inline void vchan_get_all_descriptors(struct virt_dma_chan *vc,
>  {
>  	lockdep_assert_held(&vc->lock);
>  
> -	list_splice_tail_init(&vc->desc_allocated, head);
>  	list_splice_tail_init(&vc->desc_submitted, head);
>  	list_splice_tail_init(&vc->desc_issued, head);
>  	list_splice_tail_init(&vc->desc_completed, head);
>  	list_splice_tail_init(&vc->desc_terminated, head);
>  }
>  
> +/**
> + * vchan_get_all_allocated_descs - obtain all descriptors
> + * @vc: virtual channel to get descriptors from
> + * @head: list of descriptors found
> + *
> + * vc.lock must be held by caller
> + *
> + * Removes all descriptors from internal lists, and provides a list of all
> + * descriptors found
> + */
> +static inline void vchan_get_all_allocated_descs(struct virt_dma_chan *vc,
> +	struct list_head *head)
> +{
> +	list_splice_tail_init(&vc->desc_allocated, head);
> +	vchan_get_all_descriptors(vc, head);
> +}
> +
>  static inline void vchan_free_chan_resources(struct virt_dma_chan *vc)
>  {
>  	struct virt_dma_desc *vd;
> @@ -201,7 +217,7 @@ static inline void vchan_free_chan_resources(struct virt_dma_chan *vc)
>  	LIST_HEAD(head);
>  
>  	spin_lock_irqsave(&vc->lock, flags);
> -	vchan_get_all_descriptors(vc, &head);
> +	vchan_get_all_allocated_descs(vc, &head);
>  	list_for_each_entry(vd, &head, node)
>  		dmaengine_desc_clear_reuse(&vd->tx);
>  	spin_unlock_irqrestore(&vc->lock, flags);
> -- 
> 2.33.0
>