Re: [PATCH] dmaengine: sun6i: fix use-after-free in descriptor error path

[Frank Li]

On Mon, Aug 10, 2026 at 10:20:44AM +0000, Chaithanya Lagisetty wrote:
> The err_lli_free cleanup loops in sun6i_dma_prep_slave_sg() and
> sun6i_dma_prep_dma_cyclic() free each LLI node with dma_pool_free()
> and then dereference the freed node to obtain v_lli_next and
> p_lli_next for the next loop iteration.
>
> Save the next pointers before freeing, matching the pattern already used
> in sun6i_dma_free_desc().
>
> Fixes: 9aa48806edb8 ("dmaengine: sun6i: Do not use virt_to_phys")
> Signed-off-by: Chaithanya Lagisetty <nagachaithanya9911@xxxxxxxxx>
> ---

Reviewed-by: Frank Li <Frank.Li@xxxxxxx>

>  drivers/dma/sun6i-dma.c | 18 ++++++++++++------
>  1 file changed, 12 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/dma/sun6i-dma.c b/drivers/dma/sun6i-dma.c
> index f47a326dd7ff..2439fa6564f2 100644
> --- a/drivers/dma/sun6i-dma.c
> +++ b/drivers/dma/sun6i-dma.c
> @@ -720,10 +720,10 @@ static struct dma_async_tx_descriptor *sun6i_dma_prep_slave_sg(
>  	struct sun6i_dma_dev *sdev = to_sun6i_dma_dev(chan->device);
>  	struct sun6i_vchan *vchan = to_sun6i_vchan(chan);
>  	struct dma_slave_config *sconfig = &vchan->cfg;
> -	struct sun6i_dma_lli *v_lli, *prev = NULL;
> +	struct sun6i_dma_lli *v_lli, *v_next, *prev = NULL;
>  	struct sun6i_desc *txd;
>  	struct scatterlist *sg;
> -	dma_addr_t p_lli;
> +	dma_addr_t p_lli, p_next;
>  	u32 lli_cfg;
>  	int i, ret;
>
> @@ -789,8 +789,11 @@ static struct dma_async_tx_descriptor *sun6i_dma_prep_slave_sg(
>
>  err_lli_free:
>  	for (p_lli = txd->p_lli, v_lli = txd->v_lli; v_lli;
> -	     p_lli = v_lli->p_lli_next, v_lli = v_lli->v_lli_next)
> +	     p_lli = p_next, v_lli = v_next) {
> +		v_next = v_lli->v_lli_next;
> +		p_next = v_lli->p_lli_next;
>  		dma_pool_free(sdev->pool, v_lli, p_lli);
> +	}
>  	kfree(txd);
>  	return NULL;
>  }
> @@ -806,9 +809,9 @@ static struct dma_async_tx_descriptor *sun6i_dma_prep_dma_cyclic(
>  	struct sun6i_dma_dev *sdev = to_sun6i_dma_dev(chan->device);
>  	struct sun6i_vchan *vchan = to_sun6i_vchan(chan);
>  	struct dma_slave_config *sconfig = &vchan->cfg;
> -	struct sun6i_dma_lli *v_lli, *prev = NULL;
> +	struct sun6i_dma_lli *v_lli, *v_next, *prev = NULL;
>  	struct sun6i_desc *txd;
> -	dma_addr_t p_lli;
> +	dma_addr_t p_lli, p_next;
>  	u32 lli_cfg;
>  	unsigned int i, periods = buf_len / period_len;
>  	int ret;
> @@ -870,8 +873,11 @@ static struct dma_async_tx_descriptor *sun6i_dma_prep_dma_cyclic(
>
>  err_lli_free:
>  	for (p_lli = txd->p_lli, v_lli = txd->v_lli; v_lli;
> -	     p_lli = v_lli->p_lli_next, v_lli = v_lli->v_lli_next)
> +	     p_lli = p_next, v_lli = v_next) {
> +		v_next = v_lli->v_lli_next;
> +		p_next = v_lli->p_lli_next;
>  		dma_pool_free(sdev->pool, v_lli, p_lli);
> +	}
>  	kfree(txd);
>  	return NULL;
>  }
> --
> 2.43.0
>