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 X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F15D1C33CB6 for ; Fri, 17 Jan 2020 10:35:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CA38C2064C for ; Fri, 17 Jan 2020 10:35:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726409AbgAQKfq (ORCPT ); Fri, 17 Jan 2020 05:35:46 -0500 Received: from bhuna.collabora.co.uk ([46.235.227.227]:38732 "EHLO bhuna.collabora.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726085AbgAQKfq (ORCPT ); Fri, 17 Jan 2020 05:35:46 -0500 Received: from [127.0.0.1] (localhost [127.0.0.1]) (Authenticated sender: dafna) with ESMTPSA id 7EA6D294794 Subject: Re: [PATCH v3] media: v4l2-core: fix a use-after-free bug of sd->devnode To: Hans Verkuil , linux-media@vger.kernel.org Cc: dafna3@gmail.com, helen.koike@collabora.com, ezequiel@collabora.com, stable@vger.kernel.org References: <20191120122217.845-1-dafna.hirschfeld@collabora.com> From: Dafna Hirschfeld Message-ID: Date: Fri, 17 Jan 2020 12:35:20 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org Hi On 16.01.20 13:57, Hans Verkuil wrote: > On 11/20/19 1:22 PM, Dafna Hirschfeld wrote: >> sd->devnode is released after calling >> v4l2_subdev_release. Therefore it should be set >> to NULL so that the subdev won't hold a pointer >> to a released object. This fixes a reference >> after free bug in function >> v4l2_device_unregister_subdev >> >> Cc: stable@vger.kernel.org >> Fixes: 0e43734d4c46e ("media: v4l2-subdev: add release() internal op") >> Signed-off-by: Dafna Hirschfeld >> Reviewed-by: Ezequiel Garcia >> --- >> changes since v2: >> - since this is a regresion fix, I added Fixes and Cc to stable tags, >> - change the commit title and log to be more clear. >> >> drivers/media/v4l2-core/v4l2-device.c | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/drivers/media/v4l2-core/v4l2-device.c b/drivers/media/v4l2-core/v4l2-device.c >> index 63d6b147b21e..2b3595671d62 100644 >> --- a/drivers/media/v4l2-core/v4l2-device.c >> +++ b/drivers/media/v4l2-core/v4l2-device.c >> @@ -177,6 +177,7 @@ static void v4l2_subdev_release(struct v4l2_subdev *sd) >> { >> struct module *owner = !sd->owner_v4l2_dev ? sd->owner : NULL; >> >> + sd->devnode = NULL; >> if (sd->internal_ops && sd->internal_ops->release) >> sd->internal_ops->release(sd); > > I'd move the sd->devnode = NULL; line here. That way the > sd->internal_ops->release(sd) callback can still use it. > > Unless I am missing something? It makes sense although none of the drivers uses this callback since the subdevice should be released in the v4l2_device's release so it seems that this callback can (should?) be removed. Dafna > >> module_put(owner); >> > > Regards, > > Hans >