Re: [PATCH net] net: ethernet: mtk_eth_soc: fix uninitialized variable

Simon Horman
2023-09-07T16:21:42Z

On Thu, Sep 07, 2023 at 04:14:20PM +0100, Daniel Golle wrote:
> Variable dma_addr in function mtk_poll_rx can be uninitialized on
> some of the error paths. In practise this doesn't matter, even random
> data present in uninitialized stack memory can safely be used in the
> way it happens in the error path.
>
> However, in order to make Smatch happy make sure the variable is
> always initialized.
>
> Signed-off-by: Daniel Golle <daniel@makrotopia.org>
> ---
> drivers/net/ethernet/mediatek/mtk_eth_soc.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> index 31090490d47ce..6342eac90793e 100644
> --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> @@ -2119,11 +2119,11 @@ static int mtk_poll_rx(struct napi_struct *napi, int budget,
> u8 *data, *new_data;
> struct mtk_rx_dma_v2 *rxd, trxd;
> int done = 0, bytes = 0;
> + dma_addr_t dma_addr = NULL;

Hi Daniel,

I'm not sure that NULL is a valid value for a variable of type dma_addr_t.
Is DMA_MAPPING_ERROR more appropriate here?

Flagged by Sparse and, W=1 builds with gcc-13 and clang-16.

>
> while (done < budget) {
> unsigned int pktlen, *rxdcsum;
> struct net_device *netdev;
> - dma_addr_t dma_addr;
> u32 hash, reason;
> int mac = 0;
>
> --
> 2.42.0
>