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In-Reply-To: <20200317165729.GQ2363188@phenom.ffwll.local>
From:   Qiujun Huang <hqjagain@gmail.com>
Date:   Wed, 18 Mar 2020 06:29:02 +0800
Message-ID: <CAJRQjod6JD8AGtBRxpsGJV3ACd0QLO_UvNDeM1rMuZPioAqB4A@mail.gmail.com>
Subject: Re: [PATCH] drm/lease: fix WARNING in idr_destroy
To:     Qiujun Huang <hqjagain@gmail.com>,
        maarten.lankhorst@linux.intel.com, mripard@kernel.org,
        airlied@linux.ie, dri-devel@lists.freedesktop.org,
        LKML <linux-kernel@vger.kernel.org>
Cc:     Daniel Vetter <daniel@ffwll.ch>
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On Wed, Mar 18, 2020 at 12:57 AM Daniel Vetter <daniel@ffwll.ch> wrote:
>
> On Mon, Mar 16, 2020 at 11:36:08AM +0800, Qiujun Huang wrote:
> > leases has been destroyed:
> > drm_master_put
> >     ->drm_master_destroy
> >             ->idr_destroy
> >
> > so the "out_lessee" needn't to call idr_destroy again.
> >
> > Reported-and-tested-by: syzbot+05835159fe322770fe3d@syzkaller.appspotmail.com
> > Signed-off-by: Qiujun Huang <hqjagain@gmail.com>
> > ---
> >  drivers/gpu/drm/drm_lease.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/drm_lease.c b/drivers/gpu/drm/drm_lease.c
> > index b481caf..54506c2 100644
> > --- a/drivers/gpu/drm/drm_lease.c
> > +++ b/drivers/gpu/drm/drm_lease.c
> > @@ -577,11 +577,14 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev,
> >
> >  out_lessee:
> >       drm_master_put(&lessee);
> > +     goto err_exit;
>
> I think this is correct, but also confusioning and inconsistent with the
> existing style. Most error cases before drm_lease_create explicit destroy
> the idr, except the one for drm_lease_create.
Yeah, it is.

>
> Instead of your patch I'd
> - remove the idr_destry from the error unrolling here
> - add it the to drm_lease_create error case
> - add a comment above the call to drm_lease_crete that it takes ownership
>   of the lease idr
>
> Can you pls respin and retest to make sure that patch is still correct?
I get that, thanks.

>
> Thanks, Daniel
>
> >
> >  out_leases:
> > -     put_unused_fd(fd);
> >       idr_destroy(&leases);
> >
> > +err_exit:
> > +     put_unused_fd(fd);
> > +
> >       DRM_DEBUG_LEASE("drm_mode_create_lease_ioctl failed: %d\n", ret);
> >       return ret;
> >  }
> > --
> > 1.8.3.1
> >
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch