linux-kernel - RE: [PATCH 2/2] tty: serial: fsl_lpuart: fix the potential bug of dereference null return value

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Date:   Mon, 26 Apr 2021 11:39:03 +0000
From:   Sherry Sun <sherry.sun@....com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     "jirislaby@...nel.org" <jirislaby@...nel.org>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>
Subject: RE: [PATCH 2/2] tty: serial: fsl_lpuart: fix the potential bug of
 dereference null return value

Hi Greg,

> -----Original Message-----
> From: Greg KH <gregkh@...uxfoundation.org>
> Sent: 2021年4月26日 16:09
> To: Sherry Sun <sherry.sun@....com>
> Cc: jirislaby@...nel.org; linux-serial@...r.kernel.org; linux-
> kernel@...r.kernel.org; dl-linux-imx <linux-imx@....com>
> Subject: Re: [PATCH 2/2] tty: serial: fsl_lpuart: fix the potential bug of
> dereference null return value
> 
> On Mon, Apr 26, 2021 at 03:49:35PM +0800, Sherry Sun wrote:
> > This issue is reported by Coverity Check.
> > In lpuart_probe, return value of function which returns null is
> > dereferenced without checking.
> >
> > Signed-off-by: Sherry Sun <sherry.sun@....com>
> > ---
> >  drivers/tty/serial/fsl_lpuart.c | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/tty/serial/fsl_lpuart.c
> > b/drivers/tty/serial/fsl_lpuart.c index 777d54b593f8..c95e71fd2ca0
> > 100644
> > --- a/drivers/tty/serial/fsl_lpuart.c
> > +++ b/drivers/tty/serial/fsl_lpuart.c
> > @@ -2589,6 +2589,9 @@ static int lpuart_probe(struct platform_device
> *pdev)
> >  	struct resource *res;
> >  	int ret;
> >
> > +	if (!sdata)
> > +		return -ENODEV;
> 
> How can sdata be NULL?

Is it possible that a case forgot to set sdata? Then the value will be NULL, such as { .compatible = "fsl,imx8qxp-lpuart",  }.
So I added the patch to avoid the kernel crash when run to sdata->reg_off directly. But I am not sure does it make sense.

Thanks again for your time.

Best regards
Sherry

> 
> thanks,
> 
> greg k-h