linux-kernel - Re: [PATCH 2/2] can: m_can: m_can_class_allocate_dev(): remove impossible error return judgment

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Message-ID: <20210205085215.sgsvtys5z4gm3ict@hardanger.blackshift.org>
Date:   Fri, 5 Feb 2021 09:52:15 +0100
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Xulin Sun <xulin.sun@...driver.com>
Cc:     wg@...ndegger.com, dmurphy@...com, sriram.dash@...sung.com,
        kuba@...nel.org, davem@...emloft.net, linux-can@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        xulinsun@...il.com
Subject: Re: [PATCH 2/2] can: m_can: m_can_class_allocate_dev(): remove
 impossible error return judgment

On 05.02.2021 16:46:16, Xulin Sun wrote:
> On 2021/2/5 下午4:19, Marc Kleine-Budde wrote:
> > On 05.02.2021 15:25:59, Xulin Sun wrote:
> > > If the previous can_net device has been successfully allocated, its
> > > private data structure is impossible to be empty, remove this redundant
> > > error return judgment. Otherwise, memory leaks for alloc_candev() will
> > > be triggered.
> > Your analysis is correct, the netdev_priv() will never fail. But how
> > will this trigger a mem leak on alloc_candev()? I've removed that
> 
> The previous code judges the netdev_priv is empty, and then goto out. The
> correct approach should add free_candev(net_dev) before goto.
> 
> The code Like:
> 
>         class_dev = netdev_priv(net_dev);
>         if (!class_dev) {
>                 dev_err(dev, "Failed to init netdev cdevate");
> +               free_candev(net_dev);
>                 goto out;
>         }
> 
> Otherwise, memory leaks for alloc_candev() will be triggered.

No - as you said in the original patch description. The return value
of netdev_priv() cannot be NULL, as net_dev is not NULL.

> Now directly remove the impossible error return judgment to resolve
> the above possible issue.

Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |

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