Re: [PATCH] serial: 8250_aspeed_vuart: Fix potential NULL dereference in aspeed_vuart_probe

From: Miaoqian Lin <linmq006@gmail.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jirislaby@kernel.org>, Joel Stanley <joel@jms.id.au>,
	Andrew Jeffery <andrew@aj.id.au>,
	Zev Weiss <zev@bewilderbeest.net>,
	Johan Hovold <johan@kernel.org>,
	Yang Guang <yang.guang5@zte.com.cn>,
	linux-serial@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-aspeed@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] serial: 8250_aspeed_vuart: Fix potential NULL dereference in aspeed_vuart_probe
Date: Mon, 4 Apr 2022 23:25:38 +0800	[thread overview]
Message-ID: <20220404152538.GA35@VICKYMQLIN-NB1.localdomain> (raw)
In-Reply-To: <YksEnnyJDoL+fE5d@kroah.com>

On Mon, Apr 04, 2022 at 04:45:50PM +0200, Greg Kroah-Hartman wrote:
> On Mon, Apr 04, 2022 at 02:38:40PM +0000, Miaoqian Lin wrote:
> > platform_get_resource() may fail and return NULL, so we should
> > better check it's return value to avoid a NULL pointer dereference.
> > 
> > Fixes: 54da3e381c2b ("serial: 8250_aspeed_vuart: use UPF_IOREMAP to set up register mapping")
> > Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
> > ---
> >  drivers/tty/serial/8250/8250_aspeed_vuart.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/drivers/tty/serial/8250/8250_aspeed_vuart.c b/drivers/tty/serial/8250/8250_aspeed_vuart.c
> > index 93fe10c680fb..9d2a7856784f 100644
> > --- a/drivers/tty/serial/8250/8250_aspeed_vuart.c
> > +++ b/drivers/tty/serial/8250/8250_aspeed_vuart.c
> > @@ -429,6 +429,8 @@ static int aspeed_vuart_probe(struct platform_device *pdev)
> >  	timer_setup(&vuart->unthrottle_timer, aspeed_vuart_unthrottle_exp, 0);
> >  
> >  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > +	if (!res)
> > +		return -EINVAL;
> 
> How did you test this change was correct?

Hi,

   I look into the implementation of platform_get_resource(),
and do cross-check the usages of it in the codebase, especially
the usages in other probe function. 
And I go through some simliar bugfix commits in the revision history——
add check for return value of platform_get_resource() in probe
functions，to learn the way to fix this kind of bugs. 
But sorry I don't have the corresponding device for running test.