linux-kernel - Re: [PATCH v1 1/3] serial: 8250_exar: Avoid NULL pointer dereference at ->exit()

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Date:   Tue, 08 Jun 2021 18:09:16 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Subject: Re: [PATCH v1 1/3] serial: 8250_exar: Avoid NULL pointer
 dereference at ->exit()

On Tue, 2021-06-08 at 17:42 +0300, Andy Shevchenko wrote:
> It's possible that during ->exit() the private_data is NULL,
> for instance when there was no GPIO device instantiated.
> Due to this we may not dereference it. Add a respective check.
> 
> Note, for now ->exit() only makes sense when GPIO device
> was instantiated, that's why we may use the check for entire
> function.
> 
> Fixes: 81171e7d31a6 ("serial: 8250_exar: Constify the software nodes")
> Reported-by: Maxim Levitsky <mlevitsk@...hat.com>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>  drivers/tty/serial/8250/8250_exar.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/serial/8250/8250_exar.c b/drivers/tty/serial/8250/8250_exar.c
> index 2f49c580139b..bd4e9f6ac29c 100644
> --- a/drivers/tty/serial/8250/8250_exar.c
> +++ b/drivers/tty/serial/8250/8250_exar.c
> @@ -553,7 +553,11 @@ static void pci_xr17v35x_exit(struct pci_dev *pcidev)
>  {
>  	struct exar8250 *priv = pci_get_drvdata(pcidev);
>  	struct uart_8250_port *port = serial8250_get_port(priv->line[0]);
> -	struct platform_device *pdev = port->port.private_data;
> +	struct platform_device *pdev;
> +
> +	pdev = port->port.private_data;
> +	if (!pdev)
> +		return;
>  
>  	device_remove_software_node(&pdev->dev);
>  	platform_device_unregister(pdev);

Hi!

I just tested this patch and it does work!
Thanks a lot for fixing this that fast!

Tested-by: Maxim Levitsky <mlevitsk@...hat.com>

Best regards,
	Maxim Levitsky