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 BB8A2C433EF for ; Tue, 3 May 2022 14:27:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237066AbiECOa6 (ORCPT ); Tue, 3 May 2022 10:30:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57594 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237037AbiECOay (ORCPT ); Tue, 3 May 2022 10:30:54 -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 99A5B31910; Tue, 3 May 2022 07:27:22 -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 37F2F61642; Tue, 3 May 2022 14:27:22 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 83BB8C385AF; Tue, 3 May 2022 14:27:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1651588041; bh=U+dMHz9mvZ+8O5RCxWHI4ioZs1g/R3YqAm9YLjXH3ro=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=mTXUNdmNQF+WbQNc3W/k1ZcRihhHAhTSm7iTwc50NKSMC26QDAGtnHgmPnlwXMMWj XEbBNsePgD8bnHbEsWxAubNb5jcmiTCWrFfEsmpsnZVki+YRAKjE794FoiBQj5XiwM wUyMH1tPCJqfSa7udZg/xk87sWL3sXQC+zQ2Ip+c= Date: Tue, 3 May 2022 16:27:20 +0200 From: Greg KH To: Thadeu Lima de Souza Cascardo Cc: stable@vger.kernel.org, netdev@vger.kernel.org, kuba@kernel.org, davem@davemloft.net, jiri@resnulli.us, xiyou.wangcong@gmail.com, jhs@mojatatu.com, vladbu@mellanox.com Subject: Re: [PATCH 4.9.y] net: sched: prevent UAF on tc_ctl_tfilter when temporarily dropping rtnl_lock Message-ID: References: <20220502204924.3456590-1-cascardo@canonical.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, May 03, 2022 at 11:24:01AM -0300, Thadeu Lima de Souza Cascardo wrote: > On Tue, May 03, 2022 at 03:49:15PM +0200, Greg KH wrote: > > On Mon, May 02, 2022 at 05:49:24PM -0300, Thadeu Lima de Souza Cascardo wrote: > > > When dropping the rtnl_lock for looking up for a module, the device may be > > > removed, releasing the qdisc and class memory. Right after trying to load > > > the module, cl_ops->put is called, leading to a potential use-after-free. > > > > > > Though commit e368fdb61d8e ("net: sched: use Qdisc rcu API instead of > > > relying on rtnl lock") fixes this, it involves a lot of refactoring of the > > > net/sched/ code, complicating its backport. > > > > What about 4.14.y? We can not take a commit for 4.9.y with it also > > being broken in 4.14.y, and yet fixed in 4.19.y, right? Anyone who > > updates from 4.9 to 4.14 will have a regression. > > > > thanks, > > > > greg k-h > > 4.14.y does not call cl_ops->put (the get/put and class refcount has been done > with on 4.14.y). However, on the error path after the lock has been dropped, > tcf_chain_put is called. But it does not touch the qdisc, but only the chain > and block objects, which cannot be released on a race condition, as far as I > was able to investigate. So what changed between 4.9 and 4.14 that requires this out-of-tree change to 4.9 for the issue? Shouldn't we backport that change instead of this custom one? thanks, greg k-h