dma: jz4740: Null pointer dereference

dma: jz4740: Null pointer dereference

[Stefan Agner]

Hi Lars,

While looking through different DMA drivers, just stumbled upon this
inside jz4740_dma_chan_irq:

if (chan->next_sg == chan->desc->num_sgs) {
	chan->desc = NULL;
	vchan_cookie_complete(&chan->desc->vdesc);
                                         ^ null pointer dereference
}

I'm not sure what the correct fix is, hence I thought I report it to you
as author of the driver.

--
Stefan

Re: dma: jz4740: Null pointer dereference

[Lars-Peter Clausen]

On 07/08/2014 06:41 PM, Stefan Agner wrote:
> Hi Lars,
>
> While looking through different DMA drivers, just stumbled upon this
> inside jz4740_dma_chan_irq:
>
> if (chan->next_sg == chan->desc->num_sgs) {
> 	chan->desc = NULL;
> 	vchan_cookie_complete(&chan->desc->vdesc);
>                                           ^ null pointer dereference
> }
>
> I'm not sure what the correct fix is, hence I thought I report it to you
> as author of the driver.

Hi,

Thanks for the report. Yes this is a bug and I have a fix for it. Currently 
that codepath is not exercised though (no non-cyclic users of the JZ4740 
dmaengine driver), so the fix is not critical. It will be sent upstream soon 
together which a couple of other patches for this driver.

- Lars