Re: [PATCH 2/2 v2] mtd: ubi: use put_device() if device_register fail

[arvindY]

On Thursday 15 March 2018 02:17 PM, Arvind Yadav wrote:
> On Thursday 15 March 2018 01:25 PM, Richard Weinberger wrote:
> > Am Donnerstag, 15. März 2018, 08:20:31 CET schrieb Arvind Yadav:
> > > if device_register() returned an error! Always use put_device()
> > > to give up the reference initialized.
> > Like DaveM said, there is no need to shout and use "!".
>
> I will fix this and send you update patch.
> > > Signed-off-by: Arvind Yadav <arvind.yadav.cs@xxxxxxxxx>
> > > ---
> > > change in v2:
> > >          Fix use-after-free bug. move put_device() after cdev_del().
> > >
> > >   drivers/mtd/ubi/vmt.c | 1 +
> > >   1 file changed, 1 insertion(+)
> > >
> > > diff --git a/drivers/mtd/ubi/vmt.c b/drivers/mtd/ubi/vmt.c
> > > index 3fd8d7f..93c6163 100644
> > > --- a/drivers/mtd/ubi/vmt.c
> > > +++ b/drivers/mtd/ubi/vmt.c
> > > @@ -610,6 +610,7 @@ int ubi_add_volume(struct ubi_device *ubi, struct
> > > ubi_volume *vol)
> > >
> > >   out_cdev:
> > >       cdev_del(&vol->cdev);
> > > +    put_device(&vol->dev);
> > >       return err;
> > The more I dig into device code, the more questions I have.
> > Why is cdev_del() not part of the release function?
> >
> > Thanks,
> > //richard
>
> Yes, It's should be a part release function.
>
> ~arvind

I was wrong, We can not add cdev_del() in release(vol_release)
function.
Function's ubi_create_volume and ubi_add_volume both are using
same release function to release a volume devices.
ubi_add_volume is registering character device for the volume.
So we will have to release character device here.

~arvind