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=ham 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 10D4BC33CB6 for ; Fri, 17 Jan 2020 10:52:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DD46E2083E for ; Fri, 17 Jan 2020 10:52:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726479AbgAQKwk (ORCPT ); Fri, 17 Jan 2020 05:52:40 -0500 Received: from bhuna.collabora.co.uk ([46.235.227.227]:38940 "EHLO bhuna.collabora.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726196AbgAQKwj (ORCPT ); Fri, 17 Jan 2020 05:52:39 -0500 Received: from [127.0.0.1] (localhost [127.0.0.1]) (Authenticated sender: dafna) with ESMTPSA id 89DEC294750 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> <2cf9c519-14d8-1a1d-d1b8-aea428deee5a@xs4all.nl> From: Dafna Hirschfeld Message-ID: <42767120-5a1e-bc08-8515-8598e9c3092c@collabora.com> Date: Fri, 17 Jan 2020 12:52:13 +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: <2cf9c519-14d8-1a1d-d1b8-aea428deee5a@xs4all.nl> 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 On 17.01.20 12:46, Hans Verkuil wrote: > On 1/17/20 11:35 AM, Dafna Hirschfeld wrote: >> 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. > > If nobody uses it, then I agree that it is better to remove it. ok, currently only vimc implements this callback this would change after the patchset `media: vimc: race condition fixes` will be accepted. Then I can send a patch removing it. Dafna > > Regards, > > Hans > >> >> Dafna >> >>> >>>> module_put(owner); >>>> >>> >>> Regards, >>> >>> Hans >>> >