On Tue, Jan 23, 2024 at 06:09:05AM +0000, Jason-JH Lin (林睿祥) wrote: > Hi Maxime, Daniel, > > We encountered similar issue with mediatek SoCs. > > We have found that in drm_atomic_helper_commit_rpm(), when disabling > the cursor plane, the old_state->legacy_cursor_update in > drm_atomic_wait_for_vblank() is set to true. > As the result, we are not actually waiting for a vlbank to wait for our > hardware to close the cursor plane. Subsequently, the execution > proceeds to drm_atomic_helper_cleanup_planes() to free the cursor > buffer. This can lead to use-after-free issues with our hardware. > > Could you please apply this patch to fix our problem? > Or are there any considerations for not applying this patch? Mostly it needs someone to collect a pile of acks/tested-by and then land it. I'd be _very_ happy if someone else can take care of that ... There's also the potential issue that it might slow down some of the legacy X11 use-cases that really needed a non-blocking cursor, but I think all the drivers where this matters have switched over to the async plane update stuff meanwhile. So hopefully that's good. Cheers, Sima > > Regards, > Jason-JH.Lin > > On Tue, 2023-03-07 at 15:56 +0100, Maxime Ripard wrote: > > Hi, > > > > On Thu, Feb 16, 2023 at 12:12:13PM +0100, Daniel Vetter 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. > > > > Thanks for submitting that patch. It's been in the downstream RPi > > tree > > for a while, so I'd really like it to be merged eventually :) > > > > Acked-by: Maxime Ripard <maxime@xxxxxxxxxx> > > > > Maxime -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
