Re: [PATCH 1/4] dmaengine: zynqmp_dma: Typecast the variable to handle overflow

From: Vinod Koul
Date: Mon Oct 25 2021 - 02:10:45 EST


On 14-09-21, 13:58, Harini Katakam wrote:
> From: Shravya Kumbham <shravya.kumbham@xxxxxxxxxx>
>
> In zynqmp_dma_alloc/free_chan_resources functions there is a
> potential overflow in the below expressions.
>
> dma_alloc_coherent(chan->dev, (2 * chan->desc_size *
> ZYNQMP_DMA_NUM_DESCS),
> &chan->desc_pool_p, GFP_KERNEL);
>
> dma_free_coherent(chan->dev,(2 * ZYNQMP_DMA_DESC_SIZE(chan) *
> ZYNQMP_DMA_NUM_DESCS),
> chan->desc_pool_v, chan->desc_pool_p);
>
> The arguments desc_size and ZYNQMP_DMA_NUM_DESCS are 32 bit. Though
> this overflow condition is not observed but it is a potential problem
> in the case of 32-bit multiplication. Hence fix it by using typecast.
>
> Addresses-Coverity: Event overflow_before_widen.
> Signed-off-by: Shravya Kumbham <shravya.kumbham@xxxxxxxxxx>

Patch was sent by Harini Katakam <harini.katakam@xxxxxxxxxx> and SOB not
available for person sending this patch, sorry cant accept it with
s-o-b...

> Reviewed-by: Radhey Shyam Pandey <radhey.shyam.pandey@xxxxxxxxxx>
> ---
> drivers/dma/xilinx/zynqmp_dma.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/dma/xilinx/zynqmp_dma.c b/drivers/dma/xilinx/zynqmp_dma.c
> index 5fecf5aa6e85..2d0eba25739d 100644
> --- a/drivers/dma/xilinx/zynqmp_dma.c
> +++ b/drivers/dma/xilinx/zynqmp_dma.c
> @@ -490,7 +490,8 @@ static int zynqmp_dma_alloc_chan_resources(struct dma_chan *dchan)
> }
>
> chan->desc_pool_v = dma_alloc_coherent(chan->dev,
> - (2 * chan->desc_size * ZYNQMP_DMA_NUM_DESCS),
> + ((size_t)(2 * chan->desc_size) *
> + ZYNQMP_DMA_NUM_DESCS),
> &chan->desc_pool_p, GFP_KERNEL);
> if (!chan->desc_pool_v)
> return -ENOMEM;
> @@ -677,7 +678,8 @@ static void zynqmp_dma_free_chan_resources(struct dma_chan *dchan)
> zynqmp_dma_free_descriptors(chan);
> spin_unlock_irqrestore(&chan->lock, irqflags);
> dma_free_coherent(chan->dev,
> - (2 * ZYNQMP_DMA_DESC_SIZE(chan) * ZYNQMP_DMA_NUM_DESCS),
> + ((size_t)(2 * ZYNQMP_DMA_DESC_SIZE(chan)) *
> + ZYNQMP_DMA_NUM_DESCS),
> chan->desc_pool_v, chan->desc_pool_p);
> kfree(chan->sw_desc_pool);
> pm_runtime_mark_last_busy(chan->dev);
> --
> 2.17.1

--
~Vinod