[PATCH v2] staging: gpib: cb7210: Add error handling

[PATCH v2] staging: gpib: cb7210: Add error handling

[Nihar Chaithanya]

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@gmail.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;
-
+	}
 	return 0;
 }
 
-- 
2.34.1

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

[Greg KH]

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@gmail.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

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

[Greg KH]

On Sat, Dec 21, 2024 at 10:25:41AM +0100, Greg KH wrote:
> 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@gmail.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.

And (this is taking you down a path that is much larger than you
expected to just fix this one issue, sorry), it looks like
gpib_register_driver() can fail, so it MUST return an error value so you
can properly unwind from it.  So that too needs to be fixed up here
(also minor nit, gpib_register_driver() should not be calling pr_info(),
but that's a different issue.)

In all, there are loads of tiny things like this to fix up in the gpib
code, which is great, have fun!

thanks,

greg k-h

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

[Nihar Chaithanya]

On 21/12/24 15:13, Greg KH wrote:
> On Sat, Dec 21, 2024 at 10:25:41AM +0100, Greg KH wrote:
>> 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@gmail.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 I need be unregistering the driver if the pcmcia_register_driver() fails
right?
>> 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.
> And (this is taking you down a path that is much larger than you
> expected to just fix this one issue, sorry), it looks like
> gpib_register_driver() can fail, so it MUST return an error value so you
> can properly unwind from it.  So that too needs to be fixed up here
> (also minor nit, gpib_register_driver() should not be calling pr_info(),
> but that's a different issue.)
Yes Greg, gpib_register_driver() should be returning -ENOMEM if it fails,
thank you for pointing it out, I'll change the gpib code wherever the
drivers are registered, I'll send the patch as soon as I can.
> In all, there are loads of tiny things like this to fix up in the gpib
> code, which is great, have fun!
yes, I am happy to contribute.
> thanks,
>
> greg k-h
thank you,
Nihar

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

[Greg KH]

On Sat, Dec 21, 2024 at 04:59:31PM +0530, Nihar Chaithanya wrote:
> 
> On 21/12/24 15:13, Greg KH wrote:
> > On Sat, Dec 21, 2024 at 10:25:41AM +0100, Greg KH wrote:
> > > 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@gmail.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 I need be unregistering the driver if the pcmcia_register_driver() fails
> right?

Yes, all of them.

thanks,

greg k-h