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Date:   Fri, 5 Feb 2021 09:52:15 +0100
From:   Marc Kleine-Budde <mkl@pengutronix.de>
To:     Xulin Sun <xulin.sun@windriver.com>
Cc:     wg@grandegger.com, dmurphy@ti.com, sriram.dash@samsung.com,
        kuba@kernel.org, davem@davemloft.net, linux-can@vger.kernel.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        xulinsun@gmail.com
Subject: Re: [PATCH 2/2] can: m_can: m_can_class_allocate_dev(): remove
 impossible error return judgment
Message-ID: <20210205085215.sgsvtys5z4gm3ict@hardanger.blackshift.org>
References: <20210205072559.13241-1-xulin.sun@windriver.com>
 <20210205072559.13241-2-xulin.sun@windriver.com>
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On 05.02.2021 16:46:16, Xulin Sun wrote:
> On 2021/2/5 =E4=B8=8B=E5=8D=884:19, 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 redunda=
nt
> > > 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
>=20
> The previous code judges the netdev_priv is empty, and then goto out. The
> correct approach should add free_candev(net_dev) before goto.
>=20
> The code Like:
>=20
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 class_dev =3D netdev_priv(net_=
dev);
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (!class_dev) {
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0 dev_err(dev, "Failed to init netdev cdevate");
> +=C2=A0=C2=A0=C2=A0=C2=A0 =C2=A0 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0 free_candev(net_dev);
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0 goto out;
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 }
>=20
> 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

--=20
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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