[bug report] mtd: rawnand: cadence: fix DMA device NULL pointer dereference

[Niravkumar L Rabara]

On 27/10/2025 2:36 pm, Dan Carpenter wrote:
> Hello Niravkumar L Rabara,
> 
> This is a semi-automatic email about new static checker warnings.
> 
> Commit 5c56bf214af8 ("mtd: rawnand: cadence: fix DMA device NULL
> pointer dereference") from Oct 23, 2025, leads to the following
> Smatch complaint:
> 
>      drivers/mtd/nand/raw/cadence-nand-controller.c:2956 cadence_nand_init()
>      warn: variable dereferenced before check 'cdns_ctrl->dmac' (see line 2918)
> 
> drivers/mtd/nand/raw/cadence-nand-controller.c
>    2909          if (cdns_ctrl->caps1->has_dma) {
>    2910                  cdns_ctrl->dmac = dma_request_chan_by_mask(&mask);
>                          ^^^^^^^^^^^^^^^
> This is only set sometimes
> 
> 
>    2911                  if (IS_ERR(cdns_ctrl->dmac)) {
>    2912                          ret = dev_err_probe(cdns_ctrl->dev, PTR_ERR(cdns_ctrl->dmac),
>    2913                                              "%d: Failed to get a DMA channel\n", ret);
>    2914                          goto disable_irq;
>    2915                  }
>    2916          }
>    2917
>    2918          dma_dev = cdns_ctrl->dmac->device;
>                            ^^^^^^^^^^^^^^^^^
> Potential NULL dereference
> 
>    2919          cdns_ctrl->io.iova_dma = dma_map_resource(dma_dev->dev, cdns_ctrl->io.dma,
>    2920                                                    cdns_ctrl->io.size,

>    2954
>    2955  dma_release_chnl:
>    2956          if (cdns_ctrl->dmac)
>                      ^^^^^^^^^^^^^^^
> Checked here, after dereference.
> 
>    2957                  dma_release_channel(cdns_ctrl->dmac);
>    2958
> 
> 
> regards,
> dan carpenter

Dan thanks for the bug report, next time I will make sure to check using 
smatch before submitting the patch.

I will submit a patch to fix this.

Thanks,
Nirav