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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,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 479B5C468BD for ; Mon, 10 Jun 2019 03:24:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1F006207E0 for ; Mon, 10 Jun 2019 03:24:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387584AbfFJDY0 (ORCPT ); Sun, 9 Jun 2019 23:24:26 -0400 Received: from mail.cn.fujitsu.com ([183.91.158.132]:16421 "EHLO heian.cn.fujitsu.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2387483AbfFJDYZ (ORCPT ); Sun, 9 Jun 2019 23:24:25 -0400 X-IronPort-AV: E=Sophos;i="5.63,572,1557158400"; d="scan'208";a="66690332" Received: from unknown (HELO cn.fujitsu.com) ([10.167.33.5]) by heian.cn.fujitsu.com with ESMTP; 10 Jun 2019 11:24:14 +0800 Received: from G08CNEXCHPEKD03.g08.fujitsu.local (unknown [10.167.33.85]) by cn.fujitsu.com (Postfix) with ESMTP id 5D60E4CDD44A; Mon, 10 Jun 2019 11:24:11 +0800 (CST) Received: from localhost.localdomain (10.167.226.33) by G08CNEXCHPEKD03.g08.fujitsu.local (10.167.33.89) with Microsoft SMTP Server (TLS) id 14.3.439.0; Mon, 10 Jun 2019 11:24:15 +0800 From: Su Yanjun To: , , , CC: , , , Su Yanjun Subject: [PATCH] sctp: Add rcu lock to protect dst entry in sctp_transport_route Date: Mon, 10 Jun 2019 11:20:00 +0800 Message-ID: <1560136800-17961-1-git-send-email-suyj.fnst@cn.fujitsu.com> X-Mailer: git-send-email 2.7.4 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.167.226.33] X-yoursite-MailScanner-ID: 5D60E4CDD44A.ADDBD X-yoursite-MailScanner: Found to be clean X-yoursite-MailScanner-From: suyj.fnst@cn.fujitsu.com Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org syzbot found a crash in rt_cache_valid. Problem is that when more threads release dst in sctp_transport_route, the route cache can be freed. As follows, p1: sctp_transport_route dst_release get_dst p2: sctp_transport_route dst_release get_dst ... If enough threads calling dst_release will cause dst->refcnt==0 then rcu softirq will reclaim the dst entry,get_dst then use the freed memory. This patch adds rcu lock to protect the dst_entry here. Fixes: 6e91b578bf3f("sctp: re-use sctp_transport_pmtu in sctp_transport_route") Signed-off-by: Su Yanjun Reported-by: syzbot+a9e23ea2aa21044c2798@syzkaller.appspotmail.com --- net/sctp/transport.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/net/sctp/transport.c b/net/sctp/transport.c index ad158d3..5ad7e20 100644 --- a/net/sctp/transport.c +++ b/net/sctp/transport.c @@ -308,8 +308,13 @@ void sctp_transport_route(struct sctp_transport *transport, struct sctp_association *asoc = transport->asoc; struct sctp_af *af = transport->af_specific; + /* When dst entry is being released, route cache may be referred + * again. Add rcu lock here to protect dst entry. + */ + rcu_read_lock(); sctp_transport_dst_release(transport); af->get_dst(transport, saddr, &transport->fl, sctp_opt2sk(opt)); + rcu_read_unlock(); if (saddr) memcpy(&transport->saddr, saddr, sizeof(union sctp_addr)); -- 2.7.4