linux-kernel - Re: [PATCH] net: hinic: Fix warning-hinic_set_vlan_fliter() warn: variable dereferenced before check 'hwdev'

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Message-ID: <dfcf35c3-8208-48fc-5492-97dd3b1c83fb@linux.dev>
Date:   Mon, 18 Sep 2023 13:58:30 +0100
From:   Vadim Fedorenko <vadim.fedorenko@...ux.dev>
To:     Cai Huoqing <cai.huoqing@...ux.dev>
Cc:     Dan Carpenter <dan.carpenter@...aro.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: hinic: Fix warning-hinic_set_vlan_fliter() warn:
 variable dereferenced before check 'hwdev'

On 18/09/2023 13:34, Cai Huoqing wrote:
> Fix warning, 'hwdev' is checked too late

I cannot find any spot where hwdev will be NULL. Other functions in the 
driver assume that hwdev points to proper structure always. I believe 
the proper fix will be to remove redundant check.

> 
> Fixes: 2acf960e3be6 ("net: hinic: Add support for configuration of rx-vlan-filter by ethtool")
> Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
> Closes: https://lore.kernel.org/r/202309112354.pikZCmyk-lkp@intel.com/
> Signed-off-by: Cai Huoqing <cai.huoqing@...ux.dev>
> ---
>   drivers/net/ethernet/huawei/hinic/hinic_port.c | 7 +++++--
>   1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/huawei/hinic/hinic_port.c b/drivers/net/ethernet/huawei/hinic/hinic_port.c
> index 9406237c461e..bf920c709f82 100644
> --- a/drivers/net/ethernet/huawei/hinic/hinic_port.c
> +++ b/drivers/net/ethernet/huawei/hinic/hinic_port.c
> @@ -450,8 +450,8 @@ int hinic_set_rx_vlan_offload(struct hinic_dev *nic_dev, u8 en)
>   int hinic_set_vlan_fliter(struct hinic_dev *nic_dev, u32 en)
>   {
>   	struct hinic_hwdev *hwdev = nic_dev->hwdev;
> -	struct hinic_hwif *hwif = hwdev->hwif;
> -	struct pci_dev *pdev = hwif->pdev;
> +	struct hinic_hwif *hwif;
> +	struct pci_dev *pdev;
>   	struct hinic_vlan_filter vlan_filter;
>   	u16 out_size = sizeof(vlan_filter);
>   	int err;
> @@ -459,6 +459,9 @@ int hinic_set_vlan_fliter(struct hinic_dev *nic_dev, u32 en)
>   	if (!hwdev)
>   		return -EINVAL;
>   
> +	hwif = hwdev->hwif;
> +	pdev = hwif->pdev;
> +
>   	vlan_filter.func_idx = HINIC_HWIF_FUNC_IDX(hwif);
>   	vlan_filter.enable = en;
>