[Intel-gfx] [RESEND 5/6] drm/i915: Remove pci private pointer after destroying the device private

[Chris Wilson]

Quoting Michal Wajdeczko (2018-07-16 11:32:22)
> On Mon, 16 Jul 2018 10:03:31 +0200, Chris Wilson  
> <chris at chris-wilson.co.uk> wrote:
> 
> > On an aborted module load, we unwind and free our device private - but
> > we left a dangling pointer to our privates inside the pci_device. After
> > the attempted aborted unload, we may still get a call to  
> > i915_pci_remove()
> > when the module is removed, potentially chasing stale data.
> >
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > ---
> >  drivers/gpu/drm/i915/i915_drv.c |  1 +
> >  drivers/gpu/drm/i915/i915_pci.c | 13 ++++++++++++-
> >  2 files changed, 13 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_drv.c  
> > b/drivers/gpu/drm/i915/i915_drv.c
> > index 700ffb611187..3834bd758a2e 100644
> > --- a/drivers/gpu/drm/i915/i915_drv.c
> > +++ b/drivers/gpu/drm/i915/i915_drv.c
> > @@ -1424,6 +1424,7 @@ int i915_driver_load(struct pci_dev *pdev, const  
> > struct pci_device_id *ent)
> >       drm_dev_fini(&dev_priv->drm);
> >  out_free:
> >       kfree(dev_priv);
> > +     pci_set_drvdata(pdev, NULL);
> >       return ret;
> >  }
> > diff --git a/drivers/gpu/drm/i915/i915_pci.c  
> > b/drivers/gpu/drm/i915/i915_pci.c
> > index 55543f1b0236..6a4d1388ad2d 100644
> > --- a/drivers/gpu/drm/i915/i915_pci.c
> > +++ b/drivers/gpu/drm/i915/i915_pci.c
> > @@ -674,10 +674,16 @@ MODULE_DEVICE_TABLE(pci, pciidlist);
> > static void i915_pci_remove(struct pci_dev *pdev)
> >  {
> > -     struct drm_device *dev = pci_get_drvdata(pdev);
> > +     struct drm_device *dev;
> > +
> > +     dev = pci_get_drvdata(pdev);
> > +     if (!dev) /* driver load aborted, nothing to cleanup */
> > +             return;
> >       i915_driver_unload(dev);
> >       drm_dev_put(dev);
> > +
> > +     pci_set_drvdata(pdev, NULL);
> 
> Why we can't put this inside i915_driver_release() ?
> Then it will be in sync with kfree()

It pairs here with the pci remove. The driver release callback (being
the kref_put release) can happen later. That was my other choice, but I
went with doing it here because this we have the pci device here and the
synergy with the get+test followed set. My thinking was that if we tried
to dig out the pci device in a later release function (or pci callback
after remove), that should be clearly erroneous.
-Chris