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Date: Thu, 7 Sep 2023 18:21:31 +0200
From: Simon Horman <horms@kernel.org>
To: Daniel Golle <daniel@makrotopia.org>
Cc: Dan Carpenter <dan.carpenter@linaro.org>, Felix Fietkau <nbd@nbd.name>,
	John Crispin <john@phrozen.org>, Sean Wang <sean.wang@mediatek.com>,
	Mark Lee <Mark-MC.Lee@mediatek.com>,
	Lorenzo Bianconi <lorenzo@kernel.org>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-mediatek@lists.infradead.org
Subject: Re: [PATCH net] net: ethernet: mtk_eth_soc: fix uninitialized
 variable
Message-ID: <20230907162131.GK434333@kernel.org>
References: <9918f1ae-5604-4bdc-a654-e0566ca77ad6@moroto.mountain>
 <51d1ae238aecde07b2b4fe02cdab0dc87287cd96.1694099183.git.daniel@makrotopia.org>
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In-Reply-To: <51d1ae238aecde07b2b4fe02cdab0dc87287cd96.1694099183.git.daniel@makrotopia.org>

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
>