Re: [PATCH v5 12/12] drm/drm_ioctl.c: Break ioctl when drm device not registered

[jeffy]

Hi Daniel,

On 04/07/2017 03:16 PM, Daniel Vetter wrote:
> On Thu, Apr 06, 2017 at 08:31:25PM +0800, Jeffy Chen wrote:
> > After unbinding drm, the user space may still owns the drm dev fd,
> > and may still be able to call drm ioctl.
> >
> > Add a sanity check here to prevent that from happening.
> >
> > Signed-off-by: Jeffy Chen <jeffy.chen@xxxxxxxxxxxxxx>
> > ---
> >
> > Changes in v5: None
> > Changes in v4: None
> > Changes in v3: None
> > Changes in v2: None
> >
> >   drivers/gpu/drm/drm_ioctl.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
> > index 7d6deaa..15beb11 100644
> > --- a/drivers/gpu/drm/drm_ioctl.c
> > +++ b/drivers/gpu/drm/drm_ioctl.c
> > @@ -674,7 +674,7 @@ long drm_ioctl(struct file *filp,
> >
> >   	dev = file_priv->minor->dev;
> >
> > -	if (drm_device_is_unplugged(dev))
> > +	if (drm_device_is_unplugged(dev) || !dev->registered)
>
> Shouldn't we instead automatically unplug the device in
> drm_dev_unregister, instead of sprinkling tons of drm_device_is_unplugged
> || !registered all over the place?
it looks like the drm_unplug_dev would call drm_dev_unregister...
maybe we can:
1/ replace the dev_unplug_dev in udl_drv.c to drm_dev_unregister
2/ call dev_unplug_dev in drm_dev_unregister, and remove 
drm_dev_unregister in dev_unplug_dev
3/ add a drm_plug_dev or drm_device_set_plugged, and call it in 
drm_dev_register

> That should catch a few more issues where userspace might creep into the
> driver after unregistering ...
> -Daniel
>
> >   		return -ENODEV;
> >
> >   	is_driver_ioctl = nr >= DRM_COMMAND_BASE && nr < DRM_COMMAND_END;
> > --
> > 2.1.4
> >
> >
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