linux-kernel - Re: [PATCH] bus: imx-weim: fix to avoid potential NULL pointer dereference

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Message-ID: <tencent_D90A6A9DC4DD4D576DDA5600188F47A2C206@qq.com>
Date:   Mon, 28 Aug 2023 23:03:05 +0800
From:   Zhang Shurong <zhang_shurong@...mail.com>
To:     Fabio Estevam <festevam@...il.com>
Cc:     shawnguo@...nel.org, s.hauer@...gutronix.de, kernel@...gutronix.de,
        linux-imx@....com, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] bus: imx-weim: fix to avoid potential NULL pointer dereference

在 2023年7月16日星期日 CST 上午12:38:09，Fabio Estevam 写道：
> Hi Zhang,
> 
> On Sat, Jul 15, 2023 at 12:21 PM Zhang Shurong
> 
> <zhang_shurong@...mail.com> wrote:
> > of_match_device() may fail and returns a NULL pointer.
> > 
> > Fix this by checking the return value of of_match_device.
> > 
> > Fixes: 3f98b6baad63 ("drivers: bus: imx-weim: Add support for
> > i.MX1/21/25/27/31/35/50/51/53") Signed-off-by: Zhang Shurong
> > <zhang_shurong@...mail.com>
> > ---
> > 
> >  drivers/bus/imx-weim.c | 10 +++++++---
> >  1 file changed, 7 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/bus/imx-weim.c b/drivers/bus/imx-weim.c
> > index 52a5d0447390..65402bb60c18 100644
> > --- a/drivers/bus/imx-weim.c
> > +++ b/drivers/bus/imx-weim.c
> > @@ -202,15 +202,19 @@ static int weim_timing_setup(struct device *dev,
> > struct device_node *np,> 
> >  static int weim_parse_dt(struct platform_device *pdev)
> >  {
> > 
> > -       const struct of_device_id *of_id = of_match_device(weim_id_table,
> > -                                                          &pdev->dev);
> > -       const struct imx_weim_devtype *devtype = of_id->data;
> > +       const struct of_device_id *of_id;
> > +       const struct imx_weim_devtype *devtype;
> > 
> >         int ret = 0, have_child = 0;
> >         struct device_node *child;
> >         struct weim_priv *priv;
> >         void __iomem *base;
> >         u32 reg;
> > 
> > +       of_id = of_match_device(weim_id_table, &pdev->dev);
> > +       if (!of_id)
> > +               return -EINVAL;
> 
> If there is no match the driver will not probe in the first place.
> 
> I don't think this check is needed.

Hello Fabio,

I think we can make it happen by designing the platform device in a way that 
its name aligns with that of the driver. In such a scenario, when the driver 
is probed, the of_match_device function will return null. You can verify this 
functionality by reviewing the following function:

static int platform_match(struct device *dev, struct device_driver *drv)

Best regards,
Shurong