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

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Message-ID: <YIawisbbnU4Us1eT@kroah.com>
Date:   Mon, 26 Apr 2021 14:22:34 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Sherry Sun <sherry.sun@....com>
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

On Mon, Apr 26, 2021 at 11:39:03AM +0000, Sherry Sun wrote:
> 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",  }.

If a case forgets to set that somehow, then the driver will never work
with that kernel change, so someone better not submit that update :)

No need to check for something that is impossible to hit.

thanks,

greg k-h