linux-kernel - RE: [PATCH net-next 2/2] net: txgbe: Fix unsigned comparison to zero in txgbe_calc_eeprom

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Message-ID: <031801d9b3a2$191cc510$4b564f30$@trustnetic.com>
Date:   Tue, 11 Jul 2023 10:47:56 +0800
From:   Jiawen Wu <jiawenwu@...stnetic.com>
To:     "'YueHaibing'" <yuehaibing@...wei.com>,
        <mengyuanlou@...-swift.com>, <davem@...emloft.net>,
        <edumazet@...gle.com>, <kuba@...nel.org>, <pabeni@...hat.com>
Cc:     <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH net-next 2/2] net: txgbe: Fix unsigned comparison to zero in txgbe_calc_eeprom_checksum()

On Saturday, November 5, 2022 4:07 PM, YueHaibing wrote:
> The error checks on checksum for a negative error return always fails because
> it is unsigned and can never be negative.
> 
> Fixes: 049fe5365324 ("net: txgbe: Add operations to interact with firmware")
> Signed-off-by: YueHaibing <yuehaibing@...wei.com>
> ---
>  drivers/net/ethernet/wangxun/txgbe/txgbe_hw.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/wangxun/txgbe/txgbe_hw.c b/drivers/net/ethernet/wangxun/txgbe/txgbe_hw.c
> index 9cf5fe33118e..167f7ff73192 100644
> --- a/drivers/net/ethernet/wangxun/txgbe/txgbe_hw.c
> +++ b/drivers/net/ethernet/wangxun/txgbe/txgbe_hw.c
> @@ -200,10 +200,11 @@ static int txgbe_calc_eeprom_checksum(struct txgbe_hw *hw, u16 *checksum)
>  	if (eeprom_ptrs)
>  		kvfree(eeprom_ptrs);
> 
> -	*checksum = TXGBE_EEPROM_SUM - *checksum;
> -	if (*checksum < 0)
> +	if (*checksum > TXGBE_EEPROM_SUM)
>  		return -EINVAL;
> 
> +	*checksum = TXGBE_EEPROM_SUM - *checksum;
> +
>  	return 0;
>  }

It is a pity, I didn't review this patch carefully. *checksum will sometimes
be larger than TXGBE_EEPROM_SUM. It's correct to remove these two lines:

-	if (*checksum < 0)
-		return -EINVAL;

I'll send a patch to fix it.