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

[jeffy <jeffy.chen@rock-chips.com>]

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@rock-chips.com>
>> ---
>>
>> 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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>