On Tue, Jun 19, 2018 at 5:50 PM Daniel Vetter daniel.vetter@ffwll.ch wrote:

The stuff never really worked, and leads to lots of fun because it out-of-order frees atomic states. Which upsets KASAN, among other things.

For async updates we now have a more solid solution with the ->atomic_async_check and ->atomic_async_commit hooks. Support for that for msm and vc4 landed. nouveau and i915 have their own commit routines, doing something similar.

For everyone else it's probably better to remove the use-after-free bug, and encourage folks to use the async support instead. The affected drivers which register a legacy cursor plane and don't either use the new async stuff or their own commit routine are: amdgpu, atmel, mediatek, qxl, rockchip, sti, sun4i, tegra, virtio, and vmwgfx.

Inspired by an amdgpu bug report.

References: https://bugzilla.kernel.org/show_bug.cgi?id=199425 Cc: mikita.lipski@amd.com Cc: Michel Dänzer michel@daenzer.net Cc: harry.wentland@amd.com Signed-off-by: Daniel Vetter daniel.vetter@intel.com

Any comments on this from amd's side? -Daniel

---

drivers/gpu/drm/drm_atomic_helper.c | 13 ------------- 1 file changed, 13 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c index 130da5195f3b..5a576cdf26dd 100644 --- a/drivers/gpu/drm/drm_atomic_helper.c +++ b/drivers/gpu/drm/drm_atomic_helper.c @@ -1330,13 +1330,6 @@ drm_atomic_helper_wait_for_vblanks(struct drm_device *dev, int i, ret; unsigned crtc_mask = 0;

•    /*
  

•     * Legacy cursor ioctls are completely unsynced, and userspace
  

•     * relies on that (by doing tons of cursor updates).
  

•     */
  

•   if (old_state->legacy_cursor_update)
  

•           return;
  

•   for_each_oldnew_crtc_in_state(old_state, crtc, old_crtc_state, new_crtc_state, i) {
            if (!new_crtc_state->active)
                    continue;
  

@@ -1884,12 +1877,6 @@ int drm_atomic_helper_setup_commit(struct drm_atomic_state *state, continue; }

•           /* Legacy cursor updates are fully unsynced. */
  

•           if (state->legacy_cursor_update) {
  

•                   complete_all(&commit->flip_done);
  

•                   continue;
  

•           }
  

•           if (!new_crtc_state->event) {
                    commit->event = kzalloc(sizeof(*commit->event),
                                            GFP_KERNEL);
  

-- 2.18.0.rc2