Re: [PATCH] net: iucv: Free memory obtained by kzalloc

[Arvind Yadav]

On Wednesday 28 February 2018 05:26 PM, Cornelia Huck wrote:
> On Wed, 28 Feb 2018 17:14:55 +0530
> Arvind Yadav <arvind.yadav.cs@xxxxxxxxx> wrote:
>
> > On Wednesday 28 February 2018 04:00 PM, Cornelia Huck wrote:
> > > On Wed, 28 Feb 2018 15:24:16 +0530
> > > Arvind Yadav <arvind.yadav.cs@xxxxxxxxx> wrote:
> > >   
> > > > Free memory, if afiucv_iucv_init is not successful and
> > > > removing a IUCV driver.
> > > >
> > > > Signed-off-by: Arvind Yadav <arvind.yadav.cs@xxxxxxxxx>
> > > > ---
> > > >    net/iucv/af_iucv.c | 5 ++++-
> > > >    1 file changed, 4 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/net/iucv/af_iucv.c b/net/iucv/af_iucv.c
> > > > index 1e8cc7b..eb0995a 100644
> > > > --- a/net/iucv/af_iucv.c
> > > > +++ b/net/iucv/af_iucv.c
> > > > @@ -2433,9 +2433,11 @@ static int afiucv_iucv_init(void)
> > > >    	af_iucv_dev->driver = &af_iucv_driver;
> > > >    	err = device_register(af_iucv_dev);
> > > >    	if (err)
> > > > -		goto out_driver;
> > > > +		goto out_iucv_dev;
> > > >    	return 0;
> > > >    
> > > > +out_iucv_dev:
> > > > +	kfree(af_iucv_dev);
> > > >    out_driver:
> > > >    	driver_unregister(&af_iucv_driver);
> > > >    out_iucv:
> > > > @@ -2496,6 +2498,7 @@ static void __exit afiucv_exit(void)
> > > >    {
> > > >    	if (pr_iucv) {
> > > >    		device_unregister(af_iucv_dev);
> > > > +		kfree(af_iucv_dev);
> > > >    		driver_unregister(&af_iucv_driver);
> > > >    		pr_iucv->iucv_unregister(&af_iucv_handler, 0);
> > > >    		symbol_put(iucv_if);
> > > No, you must not use kfree() after you called device_register() (even
> > > if it was not successful!) -- see the comment for device_register().
> > Yes, Your are right. First we need to call put_device() then kfree().
> > I will send updated patch.
> No, that's not correct, either. device_register() will give up any
> reference it obtained, and the caller did not obtain any additional
> reference, so a put_device() would be wrong. A kfree() on a refcounted
> structure is wrong as well.
If you will see the comment for device_register() (drivers/base/core.c)
there is mentioned that
'NOTE: _Never_ directly free @dev after calling this function, even
if it returned an error! Always use put_device() to give up the
reference initialized in this function instead.'
But as per you comment. we should not use.
Thanks,