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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5DDD3C4321E for ; Wed, 23 Nov 2022 09:15:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237284AbiKWJPi (ORCPT ); Wed, 23 Nov 2022 04:15:38 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57556 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237287AbiKWJPa (ORCPT ); Wed, 23 Nov 2022 04:15:30 -0500 Received: from madras.collabora.co.uk (madras.collabora.co.uk [IPv6:2a00:1098:0:82:1000:25:2eeb:e5ab]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E074E107E41 for ; Wed, 23 Nov 2022 01:15:29 -0800 (PST) Received: from [192.168.1.100] (2-237-20-237.ip236.fastwebnet.it [2.237.20.237]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (No client certificate requested) (Authenticated sender: kholk11) by madras.collabora.co.uk (Postfix) with ESMTPSA id 834646602A65; Wed, 23 Nov 2022 09:15:27 +0000 (GMT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1669194928; bh=4dlMANCcWyhN3x6ntNDLGRNwp8BpM4nQM3TDNFtBdfw=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=Ow7d1owJRJkE2pacH5cEMLBc2rKlw90cJG1YccvOwGKSzLKNdADVUkel2QGmQuHXF 027zKZa25m5a1qRMqzO/Dz6mJs/9YnLmmf1VybqGG1lYAi/tcJs4TcCt2qnsXV1u8q 3jIQIepgAZfGinKWunqb3ilM2I76ujcJhhglMLTsmOirEm7HyCsrBb4F9nIKDxeN6+ i+f86bICPbPXJ8TO4w8ZAlsJVmHg9ChT4KOTqkOdIx5NpwCejhFyVigDc3wwADVioU WeRvvWNhEDJV1S2rSxiOT7bVLJRz/BQCQRWlK9fAnjbtERqjzR0bEf32H2enEgLM7S H1cEfIRp9L7gQ== Message-ID: Date: Wed, 23 Nov 2022 10:15:25 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.5.0 Subject: Re: [PATCH v2] drm/mediatek: Clean dangling pointer on bind error path Content-Language: en-US To: =?UTF-8?B?TsOtY29sYXMgRi4gUi4gQS4gUHJhZG8=?= , Chun-Kuang Hu Cc: kernel@collabora.com, "Nancy . Lin" , CK Hu , Daniel Kurtz , Daniel Vetter , David Airlie , Mao Huang , Matthias Brugger , Philipp Zabel , YT Shen , dri-devel@lists.freedesktop.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org References: <20221122143949.3493104-1-nfraprado@collabora.com> From: AngeloGioacchino Del Regno In-Reply-To: <20221122143949.3493104-1-nfraprado@collabora.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Il 22/11/22 15:39, Nícolas F. R. A. Prado ha scritto: > mtk_drm_bind() can fail, in which case drm_dev_put() is called, > destroying the drm_device object. However a pointer to it was still > being held in the private object, and that pointer would be passed along > to DRM in mtk_drm_sys_prepare() if a suspend were triggered at that > point, resulting in a panic. Clean the pointer when destroying the > object in the error path to prevent this from happening. > > Fixes: 119f5173628a ("drm/mediatek: Add DRM Driver for Mediatek SoC MT8173.") > Signed-off-by: Nícolas F. R. A. Prado > > --- > > Changes in v2: > - Added Fixes tag > > drivers/gpu/drm/mediatek/mtk_drm_drv.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c > index 39a42dc8fb85..a21ff1b3258c 100644 > --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c > +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c > @@ -514,6 +514,7 @@ static int mtk_drm_bind(struct device *dev) > err_deinit: > mtk_drm_kms_deinit(drm); > err_free: > + private->drm = NULL; Sorry for not noticing that in v1, but I've rechecked this function and, while this commit does indeed actually solve the described issue, I think it's incomplete. A few lines before, we have a loop that sets private->all_drm_private[i]->drm = drm; ...so here you should do... private->drm = NULL; while (i--) /* a for loop will also do, your choice */ private->all_drm_private[i]->drm = NULL; That makes sure that you cleanup *everything* :-) Cheers, Angelo