From nobody Sat Feb 7 21:52:54 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 201E31F37D3; Mon, 6 Oct 2025 09:48:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759744099; cv=none; b=dVgMdTEbTxY3CFEruoODQVaYlkoewUvl6FOxn/HWVtgo1ecZ9kM+Bvl3c7utfOqZ6RkV40tI3iZnHeOrOPMQSE28by5D+gU4grKksCEOtnTlyd5uh3eOL5vi1jf9LDdWstz1agS294EiWsDLnSXIQvZPiqlrUU1PRDgYaKZvrAY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759744099; c=relaxed/simple; bh=11bNMYyZMUwsQqMUsvi0X3mz9BqFp/BUiE3cpj9uHmo=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=G/n6RXr0sjwhnMed+T8b399sQppvcS1iGI9aIEBl68D1WEnrHnU6HF6i4gxZ+q2lJc8ISaoWTBIirQS82Q9zuxRYNFkO5MueSY1VN9erlxQWayJTbrgvfNo7o24cbbpbLAfsV2UsY64ZHd1h3cD2cIR2p6crvDgDDFcqFii7P4c= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Ur8POXtb; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Ur8POXtb" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9BE33C4CEF5; Mon, 6 Oct 2025 09:48:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1759744098; bh=11bNMYyZMUwsQqMUsvi0X3mz9BqFp/BUiE3cpj9uHmo=; h=From:To:Cc:Subject:Date:From; b=Ur8POXtbkzOL6qjhq7MdssPEc9+vJgK2MlLDJHH5kGeZzO37hzg7/oKpSR3wJGmdz yPdejFaHMgc7Z5+vN+u+XHgdqARpXB/5UQnKM2FM3rMXa+MvwjkIFRxMTpdatfj0Z7 bkvmlzOITPBMvyXOdN0IgZxg4KlCVBS4RJPzOQrckxJx7xTAL4ZUpMsG14MpBpMedB oIiLv14nfvIsxk7IqNBr/ycF4kjkjCZGPSVMFW9+u+ZrOBBxxRN2XE/nAzUC0YD5+r EQX3ujGdZeENoFoGCpNKgzqBAF0vKrZW60mjiNC6mYkgwsouXKp/Halnfn99NV5279 EUnH8fjywB6gw== Received: from johan by xi.lan with local (Exim 4.98.2) (envelope-from ) id 1v5hpH-000000007MH-34s4; Mon, 06 Oct 2025 11:48:16 +0200 From: Johan Hovold To: Chun-Kuang Hu , Philipp Zabel Cc: David Airlie , Simona Vetter , Matthias Brugger , AngeloGioacchino Del Regno , CK Hu , Ma Ke , Sjoerd Simons , dri-devel@lists.freedesktop.org, linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org, Johan Hovold , stable@vger.kernel.org Subject: [PATCH] drm/mediatek: fix device use-after-free on unbind Date: Mon, 6 Oct 2025 11:39:37 +0200 Message-ID: <20251006093937.27869-1-johan@kernel.org> X-Mailer: git-send-email 2.49.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 i= n mtk_drm_get_all_drm_priv") Reported-by: Sjoerd Simons Link: https://lore.kernel.org/r/20251003-mtk-drm-refcount-v1-1-3b3f2813b0db= @collabora.com Cc: stable@vger.kernel.org Cc: Ma Ke Cc: AngeloGioacchino Del Regno Signed-off-by: Johan Hovold Reviewed-By: Sjoerd Simons Reviewed-by: AngeloGioacchino Del Regno Reviewed-by: CK Hu Tested-By: Sjoerd Simons Tested-by: Ritesh Raj Sarraf --- drivers/gpu/drm/mediatek/mtk_drm_drv.c | 10 ---------- 1 file changed, 10 deletions(-) diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/media= tek/mtk_drm_drv.c index 384b0510272c..a94c51a83261 100644 --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c @@ -686,10 +686,6 @@ static int mtk_drm_bind(struct device *dev) for (i =3D 0; i < private->data->mmsys_dev_num; i++) private->all_drm_private[i]->drm =3D NULL; err_put_dev: - for (i =3D 0; i < private->data->mmsys_dev_num; i++) { - /* For device_find_child in mtk_drm_get_all_priv() */ - put_device(private->all_drm_private[i]->dev); - } put_device(private->mutex_dev); return ret; } @@ -697,18 +693,12 @@ static int mtk_drm_bind(struct device *dev) static void mtk_drm_unbind(struct device *dev) { struct mtk_drm_private *private =3D dev_get_drvdata(dev); - int i; =20 /* for multi mmsys dev, unregister drm dev in mmsys master */ if (private->drm_master) { drm_dev_unregister(private->drm); mtk_drm_kms_deinit(private->drm); drm_dev_put(private->drm); - - for (i =3D 0; i < private->data->mmsys_dev_num; i++) { - /* For device_find_child in mtk_drm_get_all_priv() */ - put_device(private->all_drm_private[i]->dev); - } put_device(private->mutex_dev); } private->mtk_drm_bound =3D false; --=20 2.49.1