From patchwork Fri Dec 18 04:20:19 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: weichenchen X-Patchwork-Id: 11981141 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=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,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 11F1DC3526B for ; Fri, 18 Dec 2020 04:22:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C3C3B23A82 for ; Fri, 18 Dec 2020 04:22:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731638AbgLREVs (ORCPT ); Thu, 17 Dec 2020 23:21:48 -0500 Received: from out30-132.freemail.mail.aliyun.com ([115.124.30.132]:60751 "EHLO out30-132.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727017AbgLREVs (ORCPT ); Thu, 17 Dec 2020 23:21:48 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R161e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04400;MF=weichen.chen@linux.alibaba.com;NM=1;PH=DS;RN=14;SR=0;TI=SMTPD_---0UIz3wKA_1608265250; Received: from localhost(mailfrom:weichen.chen@linux.alibaba.com fp:SMTPD_---0UIz3wKA_1608265250) by smtp.aliyun-inc.com(127.0.0.1); Fri, 18 Dec 2020 12:21:04 +0800 From: weichenchen To: davem@davemloft.net, kuba@kernel.org Cc: liuhangbin@gmail.com, dsahern@kernel.org, jdike@akamai.com, mrv@mojatatu.com, lirongqing@baidu.com, nikolay@cumulusnetworks.com, roopa@cumulusnetworks.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, splendidsky.cwc@alibaba-inc.com, yanxu.zw@alibaba-inc.com, weichenchen Subject: [PATCH] net: neighbor: fix a crash caused by mod zero Date: Fri, 18 Dec 2020 12:20:19 +0800 Message-Id: <20201218042019.52096-1-weichen.chen@linux.alibaba.com> X-Mailer: git-send-email 2.20.1 (Apple Git-117) MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org pneigh_enqueue() tries to obtain a random delay by mod NEIGH_VAR(p, PROXY_DELAY). However, NEIGH_VAR(p, PROXY_DELAY) migth be zero at that point because someone could write zero to /proc/sys/net/ipv4/neigh/[device]/proxy_delay after the callers check it. This patch double-checks NEIGH_VAR(p, PROXY_DELAY) in pneigh_enqueue() to ensure not to take zero as modulus. Signed-off-by: weichenchen --- net/core/neighbour.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/net/core/neighbour.c b/net/core/neighbour.c index 9500d28a43b0..eb5d015c53d3 100644 --- a/net/core/neighbour.c +++ b/net/core/neighbour.c @@ -1570,9 +1570,14 @@ void pneigh_enqueue(struct neigh_table *tbl, struct neigh_parms *p, struct sk_buff *skb) { unsigned long now = jiffies; + unsigned long sched_next; - unsigned long sched_next = now + (prandom_u32() % - NEIGH_VAR(p, PROXY_DELAY)); + int delay = NEIGH_VAR(p, PROXY_DELAY); + + if (delay <= 0) + sched_next = now; + else + sched_next = now + (prandom_u32() % delay); if (tbl->proxy_queue.qlen > NEIGH_VAR(p, PROXY_QLEN)) { kfree_skb(skb);