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Date:   Sat, 12 Jun 2021 18:02:56 +0300
From:   Vladimir Oltean <olteanv@gmail.com>
To:     Colin King <colin.king@canonical.com>
Cc:     Florian Fainelli <f.fainelli@gmail.com>,
        Andrew Lunn <andrew@lunn.ch>,
        Vivien Didelot <vivien.didelot@gmail.com>,
        "David S . Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>, netdev@vger.kernel.org,
        kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] net: dsa: b53: Fix dereference of null dev
Message-ID: <20210612150256.jziw3xhk7i6fyms4@skbuf>
References: <20210612144407.60259-1-colin.king@canonical.com>
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On Sat, Jun 12, 2021 at 03:44:07PM +0100, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> Currently pointer priv is dereferencing dev before dev is being null
> checked so a potential null pointer dereference can occur. Fix this
> by only assigning and using priv if dev is not-null.
> 
> Addresses-Coverity: ("Dereference before null check")
> Fixes: 16994374a6fc ("net: dsa: b53: Make SRAB driver manage port interrupts")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
>  drivers/net/dsa/b53/b53_srab.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/dsa/b53/b53_srab.c b/drivers/net/dsa/b53/b53_srab.c
> index aaa12d73784e..e77ac598f859 100644
> --- a/drivers/net/dsa/b53/b53_srab.c
> +++ b/drivers/net/dsa/b53/b53_srab.c
> @@ -629,11 +629,13 @@ static int b53_srab_probe(struct platform_device *pdev)
>  static int b53_srab_remove(struct platform_device *pdev)
>  {
>  	struct b53_device *dev = platform_get_drvdata(pdev);
> -	struct b53_srab_priv *priv = dev->priv;
>  
> -	b53_srab_intr_set(priv, false);
> -	if (dev)
> +	if (dev) {
> +		struct b53_srab_priv *priv = dev->priv;
> +
> +		b53_srab_intr_set(priv, false);
>  		b53_switch_remove(dev);
> +	}
>  
>  	return 0;
>  }
> -- 
> 2.31.1
> 

I think the better question is how can "dev" be NULL in the first
place, since b53_srab_probe() does an unconditional platform_set_drvdata()
with what appears to be a non-NULL dev.