[PATCH v2] dmaengine: xilinx: dpdma: fix crash on zero-length cyclic transfer

[Frank Li]

On Tue, Nov 03, 2026 at 04:31:32PM +0800, Li Ximo wrote:
> From: Wang Haoran <haoranwangsec at gmail.com>
>
> When buf_len is zero, the descriptor build loop never runs, leaving the
> descriptor list empty. The following list_first_entry() on the empty list
> returns a bad pointer and causes a kernel oops.
>
> Return NULL if the descriptor list is empty after the loop.
>
> This issue was found by static analysis.
>
> Reported-by: Wang Haoran <haoranwangsec at gmail.com>
> Reported-by: Li Ximo <lixicaicai at gmail.com>
> Signed-off-by: Wang Haoran <haoranwangsec at gmail.com>
> ---

Reviewed-by: Frank Li <Frank.Li at nxp.com>

> v1: https://lore.kernel.org/r/20261023065900.3455414-1-lixicaicai@gmail.com
> v2: rewrite the commit message in simpler words as suggested by Frank
> Li; no code change.
>
>  drivers/dma/xilinx/xilinx_dpdma.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/dma/xilinx/xilinx_dpdma.c b/drivers/dma/xilinx/xilinx_dpdma.c
> index d9a3542c4..bdfa85b80 100644
> --- a/drivers/dma/xilinx/xilinx_dpdma.c
> +++ b/drivers/dma/xilinx/xilinx_dpdma.c
> @@ -730,6 +730,9 @@ xilinx_dpdma_chan_prep_cyclic(struct xilinx_dpdma_chan *chan,
>  		last = sw_desc;
>  	}
>
> +	if (list_empty(&tx_desc->descriptors))
> +		goto error;
> +
>  	sw_desc = list_first_entry(&tx_desc->descriptors,
>  				   struct xilinx_dpdma_sw_desc, node);
>  	last->hw.next_desc = lower_32_bits(sw_desc->dma_addr);
> --
> 2.30.2