linux-kernel - Re: [PATCH] drm/mediatek: fix device use-after-free on unbind

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Message-ID: <e03fb71c-5d50-40c6-b6f8-965319f472c9@collabora.com>
Date: Mon, 6 Oct 2025 12:19:54 +0200
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: Johan Hovold <johan@...nel.org>, Chun-Kuang Hu <chunkuang.hu@...nel.org>,
 Philipp Zabel <p.zabel@...gutronix.de>
Cc: David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Matthias Brugger <matthias.bgg@...il.com>, CK Hu <ck.hu@...iatek.com>,
 Ma Ke <make24@...as.ac.cn>, Sjoerd Simons <sjoerd@...labora.com>,
 dri-devel@...ts.freedesktop.org, linux-mediatek@...ts.infradead.org,
 linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] drm/mediatek: fix device use-after-free on unbind

Il 06/10/25 11:39, Johan Hovold ha scritto:
> A recent change fixed device reference leaks when looking up drm
> platform device driver data during bind() but failed to remove a partial
> fix which had been added by commit 80805b62ea5b ("drm/mediatek: Fix
> kobject put for component sub-drivers").
> 
> This results in a reference imbalance on component bind() failures and
> on unbind() which could lead to a user-after-free.
> 
> Make sure to only drop the references after retrieving the driver data
> by effectively reverting the previous partial fix.
> 
> Note that holding a reference to a device does not prevent its driver
> data from going away so there is no point in keeping the reference.
> 
> Fixes: 1f403699c40f ("drm/mediatek: Fix device/node reference count leaks in mtk_drm_get_all_drm_priv")
> Reported-by: Sjoerd Simons <sjoerd@...labora.com>
> Link: https://lore.kernel.org/r/20251003-mtk-drm-refcount-v1-1-3b3f2813b0db@collabora.com
> Cc: stable@...r.kernel.org
> Cc: Ma Ke <make24@...as.ac.cn>
> Cc: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
> Signed-off-by: Johan Hovold <johan@...nel.org>

Heh, nice!

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>