linux-kernel - Re: [PATCH] drm/mediatek: fix device leaks at bind

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Message-ID: <aLFcd1ZLr0HUm-CM@hovoldconsulting.com>
Date: Fri, 29 Aug 2025 09:53:27 +0200
From: Johan Hovold <johan@...nel.org>
To: Chun-Kuang Hu <chunkuang.hu@...nel.org>
Cc: Philipp Zabel <p.zabel@...gutronix.de>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	dri-devel@...ts.freedesktop.org, linux-mediatek@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org, "Nancy.Lin" <nancy.lin@...iatek.com>
Subject: Re: [PATCH] drm/mediatek: fix device leaks at bind

On Fri, Aug 29, 2025 at 09:49:07AM +0200, Johan Hovold wrote:
> On Fri, Aug 29, 2025 at 07:51:23AM +0800, Chun-Kuang Hu wrote:
> > Johan Hovold <johan@...nel.org> 於 2025年8月27日 週三 下午5:51寫道：
> 
> > > On Tue, Jul 22, 2025 at 11:27:22AM +0200, Johan Hovold wrote:
> > > > Make sure to drop the references to the sibling platform devices and
> > > > their child drm devices taken by of_find_device_by_node() and
> > > > device_find_child() when initialising the driver data during bind().
> > > >
> > > > Fixes: 1ef7ed48356c ("drm/mediatek: Modify mediatek-drm for mt8195 multi mmsys support")
> > > > Cc: stable@...r.kernel.org    # 6.4
> > > > Cc: Nancy.Lin <nancy.lin@...iatek.com>
> > > > Signed-off-by: Johan Hovold <johan@...nel.org>
> > >
> > > Can this one be picked up?
> > 
> > Ma Ke has sent a similar patch [1] before you. And that patch fix more things.
> > I've already pick up the final version [2].
> > 
> > [1] https://patchwork.kernel.org/project/dri-devel/patch/20250718033226.3390054-1-make24@iscas.ac.cn/
> > [2] https://git.kernel.org/pub/scm/linux/kernel/git/chunkuang.hu/linux.git/commit/?h=mediatek-drm-fixes-20250825&id=1f403699c40f0806a707a9a6eed3b8904224021a
> 
> I'm afraid that patch is completely broken and introduces a potential
> use-after-free by adding a bogus decrement of the OF node refcount.
> 
> I suggest you drop that one and pick up mine instead which is correct
> and cleaner.

I see now that that patch was included in a drm pull request for rc4.
I'll send an incremental fix instead.

Johan