fix a potential memory leak in stmmac_xdp_enable_pool()

[Jakub Kicinski]

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---
fix a potential memory leak in stmmac_xdp_enable_pool()

This patch adds xsk_pool_dma_unmap() to the error path when
stmmac_xsk_wakeup() fails, to release the DMA mapping allocated
earlier by xsk_pool_dma_map().

> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_xdp.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_xdp.c
> index d7e4db7224b0..7d89d6066ea3 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_xdp.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_xdp.c
> @@ -48,8 +48,10 @@ static int stmmac_xdp_enable_pool(struct stmmac_priv *priv,
>  		napi_enable(&ch->rxtx_napi);
>
>  		err = stmmac_xsk_wakeup(priv->dev, queue, XDP_WAKEUP_RX);
> -		if (err)
> +		if (err) {
> +			xsk_pool_dma_unmap(pool, STMMAC_RX_DMA_ATTR);
>  			return err;
> +		}

Is the error cleanup here complete? Looking at stmmac_xdp_enable_pool(),
before this point the code has already executed:

  set_bit(queue, priv->af_xdp_zc_qps);
  stmmac_enable_rx_queue(priv, queue);
  stmmac_enable_tx_queue(priv, queue);
  napi_enable(&ch->rxtx_napi);

When stmmac_xsk_wakeup() fails, the patch unmaps the DMA pool but does not
appear to reverse these other state changes. Comparing with the cleanup
sequence in stmmac_xdp_disable_pool(), should the error path also:

  - call clear_bit(queue, priv->af_xdp_zc_qps)
  - disable the queues and NAPI that were just enabled

The DMA descriptors allocated by stmmac_enable_rx_queue() and
stmmac_enable_tx_queue() would also be leaked on this error path.

>  	}
>
>  	return 0;
-- 
pw-bot: cr