linux-kernel - Re: [PATCH V2] ppdev: Add an error check in register

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Date: Sun, 7 Apr 2024 11:49:52 +0200
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: Huai-Yuan Liu <qq810974084@...il.com>, sudipm.mukherjee@...il.com,
 arnd@...db.de, gregkh@...uxfoundation.org
Cc: linux-kernel@...r.kernel.org, baijiaju1990@...look.com
Subject: Re: [PATCH V2] ppdev: Add an error check in register_device

Le 07/04/2024 à 10:03, Huai-Yuan Liu a écrit :
> 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, then jump to 'err'.
> 
> 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.
> ---
>   drivers/char/ppdev.c | 7 +++++++
>   1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/char/ppdev.c b/drivers/char/ppdev.c
> index 4c188e9e477c..ac5a93d39fbd 100644
> --- a/drivers/char/ppdev.c
> +++ b/drivers/char/ppdev.c
> @@ -300,6 +300,13 @@ static int register_device(int minor, struct pp_struct *pp)
>   	}
>   
>   	index = ida_simple_get(&ida_index, 0, 0, GFP_KERNEL);
> +	if (index < 0) {
> +		pr_warn("%s: failed to get index!\n", name);
> +		parport_put_port(port);

Hi,

I think that a new label should be added, just before the 'err' label, 
and move this parport_put_port() call there, as well as the one just 
after parport_register_dev_model().

CJ

> +		rc = index;
> +		goto err;
> +	}
> +
>   	memset(&ppdev_cb, 0, sizeof(ppdev_cb));
>   	ppdev_cb.irq_func = pp_irq;
>   	ppdev_cb.flags = (pp->flags & PP_EXCL) ? PARPORT_FLAG_EXCL : 0;