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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 D9617C2BA2B for ; Sat, 11 Apr 2020 12:21:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A57B5214D8 for ; Sat, 11 Apr 2020 12:21:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586607693; bh=SLxe7vui/sy4bL9CxI8nH4037eviKppUqHtZ57BTB3g=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=rR9C8hXzz6vglqoDuxsyz0ZhOsZHb4e7old3gg0nNPCVG6z7wryA6Lad/Lhop3KDW kQmXiYSG6QfCr50AeIKHnT5ABSfbAppTum8KHT6sF2oaa7Sj99Ct+uzDUhGklvH9FV N5JRpe4mOHkmvlblea9dDKam+i9CUuPsrD8qte5M= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728460AbgDKMVb (ORCPT ); Sat, 11 Apr 2020 08:21:31 -0400 Received: from mail.kernel.org ([198.145.29.99]:57696 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728961AbgDKMV0 (ORCPT ); Sat, 11 Apr 2020 08:21:26 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 0A324214D8; Sat, 11 Apr 2020 12:21:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586607685; bh=SLxe7vui/sy4bL9CxI8nH4037eviKppUqHtZ57BTB3g=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=h9UidwObZsgQsuQAJG2WfghUCmFy+3ZqsNfW2JN3DqYSUhHuae9ODN06Yi0AiqdQ8 zhiwDc1ZJvStxE2g/3jmjCW7NoZ2YIPz5TKw2PeMiVPyIqxx8vBySVJ6SgRFXk1zYC pkmja5U4sVXvzjYBPl/TtwYP6VfcwZCp7qH0kvro= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot+46f513c3033d592409d2@syzkaller.appspotmail.com, Thomas Gleixner , "Paul E. McKenney" , Jamal Hadi Salim , Jiri Pirko , Cong Wang , "David S. Miller" Subject: [PATCH 5.6 07/38] net_sched: add a temporary refcnt for struct tcindex_data Date: Sat, 11 Apr 2020 14:09:44 +0200 Message-Id: <20200411115500.140451725@linuxfoundation.org> X-Mailer: git-send-email 2.26.0 In-Reply-To: <20200411115459.324496182@linuxfoundation.org> References: <20200411115459.324496182@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Cong Wang [ Upstream commit 304e024216a802a7dc8ba75d36de82fa136bbf3e ] Although we intentionally use an ordered workqueue for all tc filter works, the ordering is not guaranteed by RCU work, given that tcf_queue_work() is esstenially a call_rcu(). This problem is demostrated by Thomas: CPU 0: tcf_queue_work() tcf_queue_work(&r->rwork, tcindex_destroy_rexts_work); -> Migration to CPU 1 CPU 1: tcf_queue_work(&p->rwork, tcindex_destroy_work); so the 2nd work could be queued before the 1st one, which leads to a free-after-free. Enforcing this order in RCU work is hard as it requires to change RCU code too. Fortunately we can workaround this problem in tcindex filter by taking a temporary refcnt, we only refcnt it right before we begin to destroy it. This simplifies the code a lot as a full refcnt requires much more changes in tcindex_set_parms(). Reported-by: syzbot+46f513c3033d592409d2@syzkaller.appspotmail.com Fixes: 3d210534cc93 ("net_sched: fix a race condition in tcindex_destroy()") Cc: Thomas Gleixner Cc: Paul E. McKenney Cc: Jamal Hadi Salim Cc: Jiri Pirko Signed-off-by: Cong Wang Reviewed-by: Paul E. McKenney Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/sched/cls_tcindex.c | 44 ++++++++++++++++++++++++++++++++++++++------ 1 file changed, 38 insertions(+), 6 deletions(-) --- a/net/sched/cls_tcindex.c +++ b/net/sched/cls_tcindex.c @@ -11,6 +11,7 @@ #include #include #include +#include #include #include #include @@ -26,9 +27,12 @@ #define DEFAULT_HASH_SIZE 64 /* optimized for diffserv */ +struct tcindex_data; + struct tcindex_filter_result { struct tcf_exts exts; struct tcf_result res; + struct tcindex_data *p; struct rcu_work rwork; }; @@ -49,6 +53,7 @@ struct tcindex_data { u32 hash; /* hash table size; 0 if undefined */ u32 alloc_hash; /* allocated size */ u32 fall_through; /* 0: only classify if explicit match */ + refcount_t refcnt; /* a temporary refcnt for perfect hash */ struct rcu_work rwork; }; @@ -57,6 +62,20 @@ static inline int tcindex_filter_is_set( return tcf_exts_has_actions(&r->exts) || r->res.classid; } +static void tcindex_data_get(struct tcindex_data *p) +{ + refcount_inc(&p->refcnt); +} + +static void tcindex_data_put(struct tcindex_data *p) +{ + if (refcount_dec_and_test(&p->refcnt)) { + kfree(p->perfect); + kfree(p->h); + kfree(p); + } +} + static struct tcindex_filter_result *tcindex_lookup(struct tcindex_data *p, u16 key) { @@ -141,6 +160,7 @@ static void __tcindex_destroy_rexts(stru { tcf_exts_destroy(&r->exts); tcf_exts_put_net(&r->exts); + tcindex_data_put(r->p); } static void tcindex_destroy_rexts_work(struct work_struct *work) @@ -212,6 +232,8 @@ found: else __tcindex_destroy_fexts(f); } else { + tcindex_data_get(p); + if (tcf_exts_get_net(&r->exts)) tcf_queue_work(&r->rwork, tcindex_destroy_rexts_work); else @@ -228,9 +250,7 @@ static void tcindex_destroy_work(struct struct tcindex_data, rwork); - kfree(p->perfect); - kfree(p->h); - kfree(p); + tcindex_data_put(p); } static inline int @@ -248,9 +268,11 @@ static const struct nla_policy tcindex_p }; static int tcindex_filter_result_init(struct tcindex_filter_result *r, + struct tcindex_data *p, struct net *net) { memset(r, 0, sizeof(*r)); + r->p = p; return tcf_exts_init(&r->exts, net, TCA_TCINDEX_ACT, TCA_TCINDEX_POLICE); } @@ -290,6 +312,7 @@ static int tcindex_alloc_perfect_hash(st TCA_TCINDEX_ACT, TCA_TCINDEX_POLICE); if (err < 0) goto errout; + cp->perfect[i].p = cp; } return 0; @@ -334,6 +357,7 @@ tcindex_set_parms(struct net *net, struc cp->alloc_hash = p->alloc_hash; cp->fall_through = p->fall_through; cp->tp = tp; + refcount_set(&cp->refcnt, 1); /* Paired with tcindex_destroy_work() */ if (tb[TCA_TCINDEX_HASH]) cp->hash = nla_get_u32(tb[TCA_TCINDEX_HASH]); @@ -366,7 +390,7 @@ tcindex_set_parms(struct net *net, struc } cp->h = p->h; - err = tcindex_filter_result_init(&new_filter_result, net); + err = tcindex_filter_result_init(&new_filter_result, cp, net); if (err < 0) goto errout_alloc; if (old_r) @@ -434,7 +458,7 @@ tcindex_set_parms(struct net *net, struc goto errout_alloc; f->key = handle; f->next = NULL; - err = tcindex_filter_result_init(&f->result, net); + err = tcindex_filter_result_init(&f->result, cp, net); if (err < 0) { kfree(f); goto errout_alloc; @@ -447,7 +471,7 @@ tcindex_set_parms(struct net *net, struc } if (old_r && old_r != r) { - err = tcindex_filter_result_init(old_r, net); + err = tcindex_filter_result_init(old_r, cp, net); if (err < 0) { kfree(f); goto errout_alloc; @@ -571,6 +595,14 @@ static void tcindex_destroy(struct tcf_p for (i = 0; i < p->hash; i++) { struct tcindex_filter_result *r = p->perfect + i; + /* tcf_queue_work() does not guarantee the ordering we + * want, so we have to take this refcnt temporarily to + * ensure 'p' is freed after all tcindex_filter_result + * here. Imperfect hash does not need this, because it + * uses linked lists rather than an array. + */ + tcindex_data_get(p); + tcf_unbind_filter(tp, &r->res); if (tcf_exts_get_net(&r->exts)) tcf_queue_work(&r->rwork,