linux-kernel - Re: [PATCH 1/7] dmaengine: sprd: Fix the possible crash when getting engine status

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Message-ID: <20190429113555.GI3845@vkoul-mobl.Dlink>
Date:   Mon, 29 Apr 2019 17:05:55 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Baolin Wang <baolin.wang@...aro.org>
Cc:     dan.j.williams@...el.com, eric.long@...soc.com,
        orsonzhai@...il.com, zhang.lyra@...il.com, broonie@...nel.org,
        dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/7] dmaengine: sprd: Fix the possible crash when getting
 engine status

On 15-04-19, 20:14, Baolin Wang wrote:
> We will get a NULL virtual descriptor by vchan_find_desc() when the descriptor
> has been submitted, that will crash the kernel when getting the engine status.

No that is wrong, status is for descriptor and not engine!

> In this case, since the descriptor has been submitted, which means the pointer
> 'schan->cur_desc' will point to the current descriptor, then we can use
> 'schan->cur_desc' to get the engine status to avoid this issue.

Nope, since the descriptor is completed, you return with residue as 0
and DMA_COMPLETE status!

> 
> Signed-off-by: Baolin Wang <baolin.wang@...aro.org>
> ---
>  drivers/dma/sprd-dma.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/dma/sprd-dma.c b/drivers/dma/sprd-dma.c
> index 48431e2..e29342a 100644
> --- a/drivers/dma/sprd-dma.c
> +++ b/drivers/dma/sprd-dma.c
> @@ -625,7 +625,7 @@ static enum dma_status sprd_dma_tx_status(struct dma_chan *chan,
>  		else
>  			pos = 0;
>  	} else if (schan->cur_desc && schan->cur_desc->vd.tx.cookie == cookie) {
> -		struct sprd_dma_desc *sdesc = to_sprd_dma_desc(vd);
> +		struct sprd_dma_desc *sdesc = schan->cur_desc;
>  
>  		if (sdesc->dir == DMA_DEV_TO_MEM)
>  			pos = sprd_dma_get_dst_addr(schan);
> -- 
> 1.7.9.5

-- 
~Vinod