Hi Daniel, On 04/07/2017 02:30 PM, Daniel Vetter wrote: > On Thu, Apr 6, 2017 at 1:09 PM, jeffy <jeffy.chen at rock-chips.com> wrote: >> >> On 04/06/2017 04:26 PM, Daniel Vetter wrote: >>> >>> On Wed, Apr 05, 2017 at 12:28:40PM -0400, Sean Paul wrote: >>>> >>>> On Wed, Apr 05, 2017 at 04:29:26PM +0800, Jeffy Chen wrote: >>>>> >>>>> After unbinding drm, the userspace may still has a chance to access >>>>> gem buf. >>>>> >>>>> Add a sanity check for a NULL dev_private to prevent that from >>>>> happening. >>>> >>>> >>>> I still don't understand how this is happening. You're saying that these >>>> hooks >>>> can be called after rockchip_drm_unbind() has finished? >>> >>> >>> Yeah this is supposed to be impossible. If it isn't, we need to debug and >>> fix this properly. This smells like pretty bad duct-tape ... >> >> >> it looks like after unbind, the user space may still own drm dev fd, and >> could be able to call ioctl: >> lrwx------. 1 chronos chronos 64 Mar 15 12:53 28 -> /dev/dri/card1 (deleted) >> >> and the drm_unplug_dev may help it, maybe we should call it in unbind? or >> just break drm_ioctl when drm_dev not registered? > > Yes, by default unbind while userspace is running is totally broken in > drm. drm_unplug_dev would be the fix, but it's only used by udl and > not many use that. You might need to fix infrastructure up a bit. please check this patch: 9667071 New [v5,12/12] drm/drm_ioctl.c: Break ioctl when drm device not registered > > For normal module unload the module reference will prevent unloading. > So why exactly do you care about the unbind use-case? sometimes we use unbind/bind for testing ;) > -Daniel >
