linux-kernel - Re: [PATCH][V2] net: stmmac: ensure jumbo_frm error return is correctly checked for -ve value

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Message-ID: <alpine.DEB.2.20.1706051119210.2010@hadrien>
Date:   Mon, 5 Jun 2017 11:20:19 +0200 (CEST)
From:   Julia Lawall <julia.lawall@...6.fr>
To:     Colin King <colin.king@...onical.com>
cc:     Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        netdev@...r.kernel.org, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH][V2] net: stmmac: ensure jumbo_frm error return is
 correctly checked for -ve value



On Mon, 5 Jun 2017, Colin King wrote:

> From: Colin Ian King <colin.king@...onical.com>
>
> The current comparison of entry < 0 will never be true since entry is an
> unsigned integer. Make entry an int to ensure -ve error return values
> from the call to jumbo_frm are correctly being caught.

Perhaps it would be good to mention that the return value of jumbo_frm
is an int and that the subsequent computations on entry are all on small
values so there is no need for unsigned.

julia

>
> Detected by CoverityScan, CID#1238760 ("Macro compares unsigned to 0")
>
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index 68a188e74c54..3346a99ce4c4 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -2945,7 +2945,8 @@ static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev)
>  	int i, csum_insertion = 0, is_jumbo = 0;
>  	u32 queue = skb_get_queue_mapping(skb);
>  	int nfrags = skb_shinfo(skb)->nr_frags;
> -	unsigned int entry, first_entry;
> +	int entry;
> +	unsigned int first_entry;
>  	struct dma_desc *desc, *first;
>  	struct stmmac_tx_queue *tx_q;
>  	unsigned int enh_desc;
> --
> 2.11.0
>
> --
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