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

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Date:   Mon, 29 Apr 2019 19:49:04 +0800
From:   Baolin Wang <baolin.wang@...aro.org>
To:     Vinod Koul <vkoul@...nel.org>
Cc:     Dan Williams <dan.j.williams@...el.com>, eric.long@...soc.com,
        Orson Zhai <orsonzhai@...il.com>,
        Chunyan Zhang <zhang.lyra@...il.com>,
        Mark Brown <broonie@...nel.org>, dmaengine@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/7] dmaengine: sprd: Fix the possible crash when getting
 engine status

Hi Vinod,

On Mon, 29 Apr 2019 at 19:36, Vinod Koul <vkoul@...nel.org> wrote:
>
> 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!

Sure, will fix the commit message.

>
> > 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!

No, the descriptor is not completed now. If it is completed, we will
return 0 with DMA_COMPLETE status. But now the descriptor is on
progress, we should get the descriptor to return current residue.
Sorry for confusing description.

>
> >
> > 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



-- 
Baolin Wang
Best Regards