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 9DE74C77B73 for ; Mon, 5 Jun 2023 18:01:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234922AbjFESB3 (ORCPT ); Mon, 5 Jun 2023 14:01:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33092 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235024AbjFESBW (ORCPT ); Mon, 5 Jun 2023 14:01:22 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B167910EA; Mon, 5 Jun 2023 11:00:55 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 83077628E4; Mon, 5 Jun 2023 18:00:54 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 96BDEC433D2; Mon, 5 Jun 2023 18:00:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1685988053; bh=QzKDnromzr6o+llFm1S5csDJlNa3xNImFeFTlYoWklo=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=KtxHaSMp2YWFbafHhlGHF6pUV1Teos2yRuiFqv24KtoTfse5mHSTqXapqsataBVNB rs71h69BOcTVNBToYl/GzbVc+CPg/Bg3dQ8vKAQZ/j5i9LEjTnYv3a6ruotKUezESl 2jnGYAdBMM/6fCOI2nrqp+BTog8im4jQ3ycbXo7PFxLIj2qXFeGRa4M/L7cl0TGZ14 f9BoeHIxyqZ6D028ddeP1BQl24X4KjPy9mbHVf9p8tW3kK/WD0TNjSN9+UOxKaatdX 0xDs64jeFi+FJjzCZbZADUjVfX3P9r5jWZxukaHSobod+ZRNjHxQHFL+/TfgcU9iEw obnEhASd/LxFw== Date: Mon, 5 Jun 2023 19:00:46 +0100 From: Mauro Carvalho Chehab To: Thorsten Leemhuis Cc: Linux regressions mailing list , Hyunwoo Kim , Linux Media Mailing List , Thomas Voegtle , linux-kernel@vger.kernel.org Subject: Re: Sometimes DVB broken with commit 6769a0b7ee0c3b Message-ID: <20230605190046.63c98b3e@sal.lan> In-Reply-To: <88d8a7c3-0018-cc9a-13aa-e3262e20e4aa@leemhuis.info> References: <439d143b-1de7-6365-cf64-f1b44fd6d1cf@leemhuis.info> <20230605113727.69e7f309@sal.lan> <88d8a7c3-0018-cc9a-13aa-e3262e20e4aa@leemhuis.info> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.37; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org Em Mon, 5 Jun 2023 12:44:43 +0200 Thorsten Leemhuis escreveu: > On 05.06.23 12:37, Mauro Carvalho Chehab wrote: > > Em Mon, 5 Jun 2023 11:38:49 +0200 > > "Linux regression tracking (Thorsten Leemhuis)" escreveu: > > =20 > >> Hi, Thorsten here, the Linux kernel's regression tracker. > >> > >> On 30.05.23 13:12, Thomas Voegtle wrote: =20 > >>> > >>> I have the problem that sometimes my DVB card does not initialize > >>> properly booting Linux 6.4-rc4. > >>> This is not always, maybe in 3 out of 4 attempts. > >>> When this happens somehow you don't see anything special in dmesg, but > >>> the card just doesn't work. > >>> > >>> Reverting this helps: > >>> commit 6769a0b7ee0c3b31e1b22c3fadff2bfb642de23f > >>> Author: Hyunwoo Kim > >>> Date:=C2=A0=C2=A0 Thu Nov 17 04:59:22 2022 +0000 > >>> > >>> =C2=A0=C2=A0=C2=A0 media: dvb-core: Fix use-after-free on race condit= ion at dvb_frontend > >>> > >>> > >>> I have: > >>> 03:00.0 Multimedia video controller [0400]: Conexant Systems, Inc. > >>> CX23887/8 > >>> PCIe Broadcast Audio and Video Decoder with 3D Comb [14f1:8880] (rev = 04) > >>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 Subsystem: Hauppauge compu= ter works Inc. Device [0070:c138] > >>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 Kernel driver in use: cx23= 885 =20 > >> > >> Hmmm, that was posted last Tuesday and received not a single reply. :-/ > >> > >> Hyunwoo Kim: could you please look at it, as it's a regression caused = by > >> a commit of yours (one that would be good to solve before 6.4 is > >> finalized!)? And in case you are unable to do so let us know? > >> > >> But FWIW: > >> > >> Mauro: I wonder if this is something you or someone else has to look > >> into, as Hyunwoo Kim posted a few times per months to Linux lists, but > >> according to a quick search on lore hasn't posted anything since ~two > >> months now. :-/ =20 > >=20 > > Yeah, I was slow applying this one, as I was afraid of it to cause > > troubles. The DVB frontend state machine is complex, and uses a > > semaphore to update its state. There was some past attempts of > > addressing some lifetime issues there that we ended needing to revert > > or not being applied, as the fix caused more harm than good. > > [...] =20 >=20 > Thx for the update. That's unfortunate, but how it is sometimes. Which > leads to a follow-up question: is reverting the culprit temporarily an > option? Or did those old use-after-free problems became known to be a > problem we can't live with anymore for another few months? Reverting the patch seems to be the way to proceed. Then, work on another way to address UAF.=20 I'm not aware of dvb users complaining about troubles due to UAF, although= =20 it seems that there's now a CVE for it. So, maybe someone complained against a distro Kernel, which caused the CVE to be opened. So, while it is nice to have the lifetime issues fixed, last time I checked, the USB dvb-usb/dvb-usb-v2 have some logic that usually prevents it to caus= e=20 real issues during device removal, and unbinding DVB PCIe devices is=20 something that users don't do in practice. Regards, Mauro