[PATCH] ssb:: use put_device() if device_register fail

[PATCH] ssb:: use put_device() if device_register fail

[Arvind Yadav]

if device_register() returned an error! Always use put_device()
to give up the reference initialized.

Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
---
 drivers/ssb/main.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/ssb/main.c b/drivers/ssb/main.c
index 65420a9..c4449e0 100644
--- a/drivers/ssb/main.c
+++ b/drivers/ssb/main.c
@@ -521,6 +521,7 @@ static int ssb_devices_register(struct ssb_bus *bus)
 			ssb_err("Could not register %s\n", dev_name(dev));
 			/* Set dev to NULL to not unregister
 			 * dev on error unwinding. */
+			put_device(dev);
 			sdev->dev = NULL;
 			kfree(devwrap);
 			goto error;
-- 
1.9.1

Re: [PATCH] ssb:: use put_device() if device_register fail

[Michael Büsch]

[-- Attachment #1: Type: text/plain, Size: 954 bytes --]

On Wed,  7 Mar 2018 15:31:30 +0530
Arvind Yadav <arvind.yadav.cs@gmail.com> wrote:

> if device_register() returned an error! Always use put_device()
> to give up the reference initialized.
> 
> Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
> ---
>  drivers/ssb/main.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/ssb/main.c b/drivers/ssb/main.c
> index 65420a9..c4449e0 100644
> --- a/drivers/ssb/main.c
> +++ b/drivers/ssb/main.c
> @@ -521,6 +521,7 @@ static int ssb_devices_register(struct ssb_bus *bus)
>  			ssb_err("Could not register %s\n", dev_name(dev));
>  			/* Set dev to NULL to not unregister
>  			 * dev on error unwinding. */
> +			put_device(dev);
>  			sdev->dev = NULL;
>  			kfree(devwrap);
>  			goto error;


I don't think this is correct.
The dev structure is allocated as part of devwrap, which is freed here.

Why do you think we need put_device here?

-- 
Michael

[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

Re: [PATCH] ssb:: use put_device() if device_register fail

[arvindY]

On Wednesday 07 March 2018 10:17 PM, Michael Büsch wrote:
> On Wed,  7 Mar 2018 15:31:30 +0530
> Arvind Yadav <arvind.yadav.cs@gmail.com> wrote:
>
>> if device_register() returned an error! Always use put_device()
>> to give up the reference initialized.
>>
>> Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
>> ---
>>   drivers/ssb/main.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/ssb/main.c b/drivers/ssb/main.c
>> index 65420a9..c4449e0 100644
>> --- a/drivers/ssb/main.c
>> +++ b/drivers/ssb/main.c
>> @@ -521,6 +521,7 @@ static int ssb_devices_register(struct ssb_bus *bus)
>>   			ssb_err("Could not register %s\n", dev_name(dev));
>>   			/* Set dev to NULL to not unregister
>>   			 * dev on error unwinding. */
>> +			put_device(dev);
>>   			sdev->dev = NULL;
>>   			kfree(devwrap);
>>   			goto error;
>
> I don't think this is correct.
> The dev structure is allocated as part of devwrap, which is freed here.
>
> Why do you think we need put_device here?
>
Yes this patch is not correct, We must not use kfree() after you called 
device_register() (even
if it was not successful!) -- see the comment for device_register().
I will delete kfree() and send updated patch.

~arvind

Re: [PATCH] ssb:: use put_device() if device_register fail

[Michael Büsch]

[-- Attachment #1: Type: text/plain, Size: 1173 bytes --]

On Wed, 7 Mar 2018 22:46:14 +0530
arvindY <arvind.yadav.cs@gmail.com> wrote:
> >> diff --git a/drivers/ssb/main.c b/drivers/ssb/main.c
> >> index 65420a9..c4449e0 100644
> >> --- a/drivers/ssb/main.c
> >> +++ b/drivers/ssb/main.c
> >> @@ -521,6 +521,7 @@ static int ssb_devices_register(struct ssb_bus *bus)
> >>   			ssb_err("Could not register %s\n", dev_name(dev));
> >>   			/* Set dev to NULL to not unregister
> >>   			 * dev on error unwinding. */
> >> +			put_device(dev);
> >>   			sdev->dev = NULL;
> >>   			kfree(devwrap);
> >>   			goto error;  
> >
> > I don't think this is correct.
> > The dev structure is allocated as part of devwrap, which is freed here.
> >
> > Why do you think we need put_device here?
> >  
> Yes this patch is not correct, We must not use kfree() after you called 
> device_register() (even
> if it was not successful!) -- see the comment for device_register().
> I will delete kfree() and send updated patch.


Is device_put() going to call ssb_release_dev() to free the structure?

Can you please elaborate on why device_put() must be used? The comment
is not really of any use here.

-- 
Michael

[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

Re: [PATCH] ssb:: use put_device() if device_register fail

[arvindY]

On Wednesday 07 March 2018 11:08 PM, Michael Büsch wrote:
> On Wed, 7 Mar 2018 22:46:14 +0530
> arvindY <arvind.yadav.cs@gmail.com> wrote:
>>>> diff --git a/drivers/ssb/main.c b/drivers/ssb/main.c
>>>> index 65420a9..c4449e0 100644
>>>> --- a/drivers/ssb/main.c
>>>> +++ b/drivers/ssb/main.c
>>>> @@ -521,6 +521,7 @@ static int ssb_devices_register(struct ssb_bus *bus)
>>>>    			ssb_err("Could not register %s\n", dev_name(dev));
>>>>    			/* Set dev to NULL to not unregister
>>>>    			 * dev on error unwinding. */
>>>> +			put_device(dev);
>>>>    			sdev->dev = NULL;
>>>>    			kfree(devwrap);
>>>>    			goto error;
>>> I don't think this is correct.
>>> The dev structure is allocated as part of devwrap, which is freed here.
>>>
>>> Why do you think we need put_device here?
>>>   
>> Yes this patch is not correct, We must not use kfree() after you called
>> device_register() (even
>> if it was not successful!) -- see the comment for device_register().
>> I will delete kfree() and send updated patch.
>
> Is device_put() going to call ssb_release_dev() to free the structure?
>
> Can you please elaborate on why device_put() must be used? The comment
> is not really of any use here.
>
put_device() will call kobject_put(). By calling this, The kobject core 
will automatically
clean up all of the memory allocated with the kobject. Internally 
kobject_put() will call
kobject_cleanup() which is responsible to call 'dev -> release' and also 
free other
kobject resources. we should always avoid kfree() if device_register() 
returned an error.
Otherwise it'll not do clean up of other kobject resources.

~arvind