From patchwork Mon Mar 29 22:53:23 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kumar Kartikeya Dwivedi X-Patchwork-Id: 12171127 X-Patchwork-Delegate: kuba@kernel.org 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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 8A353C433EA for ; Mon, 29 Mar 2021 22:55:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6A95161999 for ; Mon, 29 Mar 2021 22:55:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231970AbhC2WzV (ORCPT ); Mon, 29 Mar 2021 18:55:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41664 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230411AbhC2WzH (ORCPT ); Mon, 29 Mar 2021 18:55:07 -0400 Received: from mail-pl1-x643.google.com (mail-pl1-x643.google.com [IPv6:2607:f8b0:4864:20::643]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 29204C061762; Mon, 29 Mar 2021 15:55:07 -0700 (PDT) Received: by mail-pl1-x643.google.com with SMTP id ay2so5141165plb.3; Mon, 29 Mar 2021 15:55:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=riwS4fKZmYi1s9ahYLZfXUq5/tOglH8JPYYvD9weK5o=; b=OR9oTxQta8eqpIy/h4iAVKRA/cVaqmQaiJDc21WMR4gHeGr9Mc2M6/9p98XGJYkB/3 b5WNjXs4c01ti+8V6SVhMejHhS8j5F4cfCZobtQBYQZco1yE2SdLNjCgAThspSE62QRc H+60liBKhyNiiFQZfuuOUeHsDikU+jcBcvTBd9XbMfdPhiASC+oQyB60To+r4aTk9vWl eKpeYpCEft1tZsDfdam5e5P4hVDma7MXKAY3Hp4RwqgPbQylCLtF84qhhd+RDiRJSYY8 lQxrZJfn6XDqR9z4fIS8BOjkT5r6L0MY3HdND4ihvr6LokMbOMRcu0BTDS0FZ5EcZyUy H1Sg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=riwS4fKZmYi1s9ahYLZfXUq5/tOglH8JPYYvD9weK5o=; b=HONxG0gnRa9QF3+iSvwMDheIJfK2+odv8lAfFdpRgvZRAMfqOtFJG3KMfJZAMD381b wxwvs3yVwpJEqqcJI0i2WKNvDaNK/uTvxcSufJbfXP4UKEZYed5Awv+saaXwMF4eUHGh XBhG0+qVShF4NHtL5OhnHvzb6uK3Mj8VXG7kkbbqEHhXpuZYFvpNvBoEEJTo/s+kSwJu AAcPpEfPMBtNaufdA2cKFikbixo6yec4yt1OIv0lKgngNgP5+ceMgBi9omLRDEpkpB5O X/Yksl5a2DHTnpIMIVS02Xu+Pq/Fk3WhJ05hPkkRzwSKbjO0V3mmCW6HgKZ17ctz88sl OvMw== X-Gm-Message-State: AOAM532N9HE9bE8r3BWtiA8zpQ+rqNkz4O8gnxWlaj4XUyeJJJ6cneql vk6x5NgO+DawJj62KpR/gQ8= X-Google-Smtp-Source: ABdhPJxuSKooLGKpUklp1sIyirkbLOMBRu9lhF2SAChgjYIOZX5GnDGW8b/pTWhxxzEC2eVO364Dlg== X-Received: by 2002:a17:90a:a4cb:: with SMTP id l11mr1298790pjw.144.1617058506536; Mon, 29 Mar 2021 15:55:06 -0700 (PDT) Received: from localhost ([112.79.230.77]) by smtp.gmail.com with ESMTPSA id q1sm9169695pgf.20.2021.03.29.15.55.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 29 Mar 2021 15:55:06 -0700 (PDT) From: Kumar Kartikeya Dwivedi To: vladbu@nvidia.com Cc: davem@davemloft.net, jhs@mojatatu.com, jiri@resnulli.us, kuba@kernel.org, linux-kernel@vger.kernel.org, memxor@gmail.com, netdev@vger.kernel.org, toke@redhat.com, xiyou.wangcong@gmail.com Subject: [PATCH v2 1/1] net: sched: bump refcount for new action in ACT replace mode Date: Tue, 30 Mar 2021 04:23:23 +0530 Message-Id: <20210329225322.143135-1-memxor@gmail.com> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org Currently, action creation using ACT API in replace mode is buggy. When invoking for non-existent action index 42, tc action replace action bpf obj foo.o sec index 42 kernel creates the action, fills up the netlink response, and then just deletes the action after notifying userspace. tc action show action bpf doesn't list the action. This happens due to the following sequence when ovr = 1 (replace mode) is enabled: tcf_idr_check_alloc is used to atomically check and either obtain reference for existing action at index, or reserve the index slot using a dummy entry (ERR_PTR(-EBUSY)). This is necessary as pointers to these actions will be held after dropping the idrinfo lock, so bumping the reference count is necessary as we need to insert the actions, and notify userspace by dumping their attributes. Finally, we drop the reference we took using the tcf_action_put_many call in tcf_action_add. However, for the case where a new action is created due to free index, its refcount remains one. This when paired with the put_many call leads to the kernel setting up the action, notifying userspace of its creation, and then tearing it down. For existing actions, the refcount is still held so they remain unaffected. Fortunately due to rtnl_lock serialization requirement, such an action with refcount == 1 will not be concurrently deleted by anything else, at best CLS API can move its refcount up and down by binding to it after it has been published from tcf_idr_insert_many. Since refcount is atleast one until put_many call, CLS API cannot delete it. Also __tcf_action_put release path already ensures deterministic outcome (either new action will be created or existing action will be reused in case CLS API tries to bind to action concurrently) due to idr lock serialization. We fix this by making refcount of newly created actions as 2 in ACT API replace mode. A relaxed store will suffice as visibility is ensured only after the tcf_idr_insert_many call. Note that in case of creation or overwriting using CLS API only (i.e. bind = 1), overwriting existing action object is not allowed, and any such request is silently ignored (without error). The refcount bump that occurs in tcf_idr_check_alloc call there for existing action will pair with tcf_exts_destroy call made from the owner module for the same action. In case of action creation, there is no existing action, so no tcf_exts_destroy callback happens. This means no code changes for CLS API. Fixes: cae422f379f3 ("net: sched: use reference counting action init") Signed-off-by: Kumar Kartikeya Dwivedi --- Changelog: v1 -> v2 Remove erroneous tcf_action_put_many call in tcf_exts_validate (Vlad) Isolate refcount bump to ACT API in replace mode --- net/sched/act_api.c | 3 +++ 1 file changed, 3 insertions(+) -- 2.30.2 diff --git a/net/sched/act_api.c b/net/sched/act_api.c index b919826939e0..43cceb924976 100644 --- a/net/sched/act_api.c +++ b/net/sched/act_api.c @@ -1042,6 +1042,9 @@ struct tc_action *tcf_action_init_1(struct net *net, struct tcf_proto *tp, if (err != ACT_P_CREATED) module_put(a_o->owner); + if (!bind && ovr && err == ACT_P_CREATED) + refcount_set(&a->tcfa_refcnt, 2); + return a; err_out: