linux-kernel - Re: [PATCH V3] ppdev: Add an error check in register

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Date: Thu, 11 Apr 2024 15:14:02 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Huai-Yuan Liu <qq810974084@...il.com>
Cc: sudipm.mukherjee@...il.com, arnd@...db.de, linux-kernel@...r.kernel.org,
	baijiaju1990@...look.com
Subject: Re: [PATCH V3] ppdev: Add an error check in register_device

On Sun, Apr 07, 2024 at 09:20:54PM +0800, Huai-Yuan Liu wrote:
> In register_device, the return value of ida_simple_get is unchecked, 
> in witch ida_simple_get will use an invalid index value.
> 
> To address this issue, index should be checked after ida_simple_get. When
> the index value is abnormal, a warning message should be printed, the port
> should be dropped, and the value should be recorded.
> 
> Fixes: 9a69645dde11 ("ppdev: fix registering same device name")
> Signed-off-by: Huai-Yuan Liu <qq810974084@...il.com>
> ---
> V2:
> * In patch V2, we found that parport_find_number implicitly calls
> parport_get_port(). So when dealing with abnormal index values, we should
> call parport_put_port() to throw away the reference to the port.
> V3:
> * In patch V3, we made some additional adjustments to the jump labels,
> making the code more concise and readable.
>   Thanks to Christophe JAILLET for helpful suggestion.
> ---
>  drivers/char/ppdev.c | 16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/char/ppdev.c b/drivers/char/ppdev.c
> index 4c188e9e477c..276db589b901 100644
> --- a/drivers/char/ppdev.c
> +++ b/drivers/char/ppdev.c
> @@ -296,28 +296,36 @@ static int register_device(int minor, struct pp_struct *pp)
>  	if (!port) {
>  		pr_warn("%s: no associated port!\n", name);
>  		rc = -ENXIO;
> -		goto err;
> +		goto err_free_name;
>  	}
>  
>  	index = ida_simple_get(&ida_index, 0, 0, GFP_KERNEL);
> +	if (index < 0) {
> +		pr_warn("%s: failed to get index!\n", name);
> +		rc = index;
> +		goto err_put_port;
> +	}
> +
>  	memset(&ppdev_cb, 0, sizeof(ppdev_cb));
>  	ppdev_cb.irq_func = pp_irq;
>  	ppdev_cb.flags = (pp->flags & PP_EXCL) ? PARPORT_FLAG_EXCL : 0;
>  	ppdev_cb.private = pp;
>  	pdev = parport_register_dev_model(port, name, &ppdev_cb, index);
> -	parport_put_port(port);
>  
>  	if (!pdev) {
>  		pr_warn("%s: failed to register device!\n", name);
>  		rc = -ENXIO;
>  		ida_simple_remove(&ida_index, index);
> -		goto err;
> +		goto err_put_port;
>  	}
>  
>  	pp->pdev = pdev;
>  	pp->index = index;
>  	dev_dbg(&pdev->dev, "registered pardevice\n");
> -err:
> +
> +err_put_port:
> +	parport_put_port(port);
> +err_free_name:
>  	kfree(name);
>  	return rc;
>  }
> -- 
> 2.34.1
> 

Does not apply to the tree at all :(