From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 2AF23CCA471 for ; Mon, 6 Oct 2025 09:48:21 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 93F4410E22E; Mon, 6 Oct 2025 09:48:20 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.b="Ur8POXtb"; dkim-atps=neutral Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by gabe.freedesktop.org (Postfix) with ESMTPS id 3B7D410E347 for ; Mon, 6 Oct 2025 09:48:19 +0000 (UTC) Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id C5D0143A7D; Mon, 6 Oct 2025 09:48:18 +0000 (UTC) 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 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" 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 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 --- 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/mediatek/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 = 0; i < private->data->mmsys_dev_num; i++) private->all_drm_private[i]->drm = NULL; err_put_dev: - for (i = 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 = dev_get_drvdata(dev); - int i; /* 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 = 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 = false; -- 2.49.1