linux-kernel - Re: [PATCH] drm/atomic-helpers: remove legacy_cursor

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <ZbKlsTEvGPiGtzS3@phenom.ffwll.local>
Date: Thu, 25 Jan 2024 19:17:21 +0100
From: Daniel Vetter <daniel@...ll.ch>
To: Jason-JH Lin (林睿祥) <Jason-JH.Lin@...iatek.com>
Cc: "maxime@...no.tech" <maxime@...no.tech>,
	"daniel.vetter@...ll.ch" <daniel.vetter@...ll.ch>,
	"manasi.d.navare@...el.com" <manasi.d.navare@...el.com>,
	"linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"michel@...nzer.net" <michel@...nzer.net>,
	"intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
	"chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
	"mikita.lipski@....com" <mikita.lipski@....com>,
	"dmitry.baryshkov@...aro.org" <dmitry.baryshkov@...aro.org>,
	"tzimmermann@...e.de" <tzimmermann@...e.de>,
	"daniel.vetter@...el.com" <daniel.vetter@...el.com>,
	"nicholas.kazlauskas@....com" <nicholas.kazlauskas@....com>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"quic_abhinavk@...cinc.com" <quic_abhinavk@...cinc.com>,
	Project_Global_Chrome_Upstream_Group <Project_Global_Chrome_Upstream_Group@...iatek.com>,
	"lucas.demarchi@...el.com" <lucas.demarchi@...el.com>,
	"sean@...rly.run" <sean@...rly.run>,
	"matthias.bgg@...il.com" <matthias.bgg@...il.com>,
	"dmitry.osipenko@...labora.com" <dmitry.osipenko@...labora.com>,
	"fshao@...omium.org" <fshao@...omium.org>,
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>,
	"jani.nikula@...el.com" <jani.nikula@...el.com>,
	"angelogioacchino.delregno@...labora.com" <angelogioacchino.delregno@...labora.com>,
	"freedreno@...ts.freedesktop.org" <freedreno@...ts.freedesktop.org>
Subject: Re: [PATCH] drm/atomic-helpers: remove legacy_cursor_update hacks

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@...no.tech>
> > 
> > Maxime

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch