Re: [PATCH] drm/drm_lease: Do not call drm_master_put() twice in case drm_lease_create() fails

[Marius-cristian Vlad <marius-cristian.vlad@nxp.com>]

drm_mode_create_lease_ioctl() -> drm_lease_create()

drm_lease_create() -> fails and drm_master_put() is called
twice: once in drm_lease_create() and once in
drm_mode_create_lease_ioctl().

From drm_mode_create_lease_ioctl():

	lessee = drm_lease_create(lessor, &leases);
        if (IS_ERR(lessee)) {
                ret = PTR_ERR(lessee);
                goto out_leases;
        }
....
out_lessee:
        drm_master_put(&lessee); <- but we already done this in
drm_lease_create().


On Tue, 2017-12-12 at 16:30 +0100, Daniel Vetter wrote:
> On Tue, Dec 12, 2017 at 02:04:14PM +0200, Marius Vlad wrote:
> > This case can been seen when creating the lease with same objects
> > passed.
> > 
> > Signed-off-by: Marius Vlad <marius-cristian.vlad@nxp.com>
> > ---
> >  drivers/gpu/drm/drm_lease.c | 2 --
> >  1 file changed, 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_lease.c
> > b/drivers/gpu/drm/drm_lease.c
> > index d1eb56a..ae57f33 100644
> > --- a/drivers/gpu/drm/drm_lease.c
> > +++ b/drivers/gpu/drm/drm_lease.c
> > @@ -254,8 +254,6 @@ static struct drm_master
> > *drm_lease_create(struct drm_master *lessor, struct idr
> >  	return lessee;
> >  
> >  out_lessee:
> > -	drm_master_put(&lessee);
> 
> I'm not really following here ... the lessee reference we're dropping
> here
> is created in drm_master_create. We're only calling drm_master_put if
> that
> succeeded. Removing this line here looks like now we're leaking.
> 
> Where is the double-free? I don't see the 2nd drm_master_put()
> anywhere
> ... drm_mode_create_lease_ioctl also seems to be doing the right
> thing
> from just staring at it.
> -Daniel
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