linux-kernel - Re: [PATCH v2] staging: gpib: cb7210: Add error handling

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Message-ID: <2024122119-unclamped-affecting-0e0a@gregkh>
Date: Sat, 21 Dec 2024 10:25:41 +0100
From: Greg KH <gregkh@...uxfoundation.org>
To: Nihar Chaithanya <niharchaithanya@...il.com>
Cc: dpenkler@...il.com, dan.carpenter@...aro.org, roheetchavan@...il.com,
	arnd@...db.de, linux-staging@...ts.linux.dev,
	linux-kernel@...r.kernel.org, skhan@...uxfoundation.org
Subject: Re: [PATCH v2] staging: gpib: cb7210: Add error handling

On Sat, Dec 21, 2024 at 02:41:25PM +0530, Nihar Chaithanya wrote:
> The if condition in cb7210_init_module() would always fail as
> the value of err is constantly 0. The function
> cb_pcmcia_init_module() can be refactored into a single line,
> and can be replaced entirely with pcmcia_register_driver().
> 
> Replace redundant cb_pcmcia_init_module() with
> pcmcia_register_driver() which returns appropriate error code if
> it fails. Handle the error if it fails and print the debug message.
> 
> This issue was reported by Coverity Scan.
> Report:
> CID 1635894: (#1 of 1): 'Constant' variable guards dead code (DEADCODE)
> dead_error_line: Execution cannot reach this statement: return -1;.
> 
> Signed-off-by: Nihar Chaithanya <niharchaithanya@...il.com>
> ---
> v1 --> v2: Replaced the redundant cb_pcmcia_init_module() with
> 	   pcmcia_register_driver().
> 
>  drivers/staging/gpib/cb7210/cb7210.c | 13 ++++---------
>  1 file changed, 4 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/staging/gpib/cb7210/cb7210.c b/drivers/staging/gpib/cb7210/cb7210.c
> index 63df7f3eb3f3..abd6632d8448 100644
> --- a/drivers/staging/gpib/cb7210/cb7210.c
> +++ b/drivers/staging/gpib/cb7210/cb7210.c
> @@ -1351,12 +1351,6 @@ static struct pcmcia_driver cb_gpib_cs_driver = {
>  	.resume		= cb_gpib_resume,
>  };
>  
> -int cb_pcmcia_init_module(void)
> -{
> -	pcmcia_register_driver(&cb_gpib_cs_driver);
> -	return 0;
> -}
> -
>  void cb_pcmcia_cleanup_module(void)
>  {
>  	DEBUG(0, "cb_gpib_cs: unloading\n");
> @@ -1526,11 +1520,12 @@ static int __init cb7210_init_module(void)
>  	gpib_register_driver(&cb_pcmcia_interface, THIS_MODULE);
>  	gpib_register_driver(&cb_pcmcia_accel_interface, THIS_MODULE);
>  	gpib_register_driver(&cb_pcmcia_unaccel_interface, THIS_MODULE);
> -	err += cb_pcmcia_init_module();
> +	err = pcmcia_register_driver(&cb_gpib_cs_driver);
>  #endif
> -	if (err)
> +	if (err) {
> +		pr_err("cb7210: registering PCMCIA driver with the bus core failed\n");
>  		return -1;

Not your issue, but "-1" is not a valid error number, shouldn't this be
returning a real error (i.e. the one that was returned?)

And err += is crazy, thanks for removing that, BUT you forgot to unwind
the previous functions so now if pcmcia_register_driver() fails, you
have a semi-registered system and then the module will unload (as init
fails) and bad things will happen :(

So you kind of just made the code worse overall, not better, which
really isn't a good idea for a "bugfix" that covertity was trying to
point out.

thanks,

greg k-h