linux-kernel - Re: [PATCH] net: ethernet: mtk-star-emac: fix error path in RX handling

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Date:   Wed, 27 May 2020 08:54:47 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Bartosz Golaszewski <brgl@...ev.pl>
Cc:     John Crispin <john@...ozen.org>,
        Sean Wang <sean.wang@...iatek.com>,
        Mark Lee <Mark-MC.Lee@...iatek.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        netdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Fabien Parent <fparent@...libre.com>,
        Stephane Le Provost <stephane.leprovost@...iatek.com>,
        Pedro Tsai <pedro.tsai@...iatek.com>,
        Andrew Perepech <andrew.perepech@...iatek.com>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH] net: ethernet: mtk-star-emac: fix error path in RX
 handling

On Wed, May 27, 2020 at 11:24:04AM +0200, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bgolaszewski@...libre.com>
> 
> The dma_addr field in desc_data must not be overwritten until after the
> new skb is mapped. Currently we do replace it with uninitialized value
> in error path. This change fixes it by moving the assignment before the
> label to which we jump after mapping or allocation errors.
> 
> Fixes: 8c7bd5a454ff ("net: ethernet: mtk-star-emac: new driver")
> Reported-by: Nathan Chancellor <natechancellor@...il.com>
> Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>

Tested-by: Nathan Chancellor <natechancellor@...il.com> # build

> ---
>  drivers/net/ethernet/mediatek/mtk_star_emac.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/mediatek/mtk_star_emac.c b/drivers/net/ethernet/mediatek/mtk_star_emac.c
> index b74349cede28..72bb624a6a68 100644
> --- a/drivers/net/ethernet/mediatek/mtk_star_emac.c
> +++ b/drivers/net/ethernet/mediatek/mtk_star_emac.c
> @@ -1308,6 +1308,8 @@ static int mtk_star_receive_packet(struct mtk_star_priv *priv)
>  		goto push_new_skb;
>  	}
>  
> +	desc_data.dma_addr = new_dma_addr;
> +
>  	/* We can't fail anymore at this point: it's safe to unmap the skb. */
>  	mtk_star_dma_unmap_rx(priv, &desc_data);
>  
> @@ -1318,7 +1320,6 @@ static int mtk_star_receive_packet(struct mtk_star_priv *priv)
>  	netif_receive_skb(desc_data.skb);
>  
>  push_new_skb:
> -	desc_data.dma_addr = new_dma_addr;
>  	desc_data.len = skb_tailroom(new_skb);
>  	desc_data.skb = new_skb;
>  
> -- 
> 2.25.0
>