From patchwork Tue Dec 22 12:38:33 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: weichenchen X-Patchwork-Id: 11986453 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 13FA6C433E6 for ; Tue, 22 Dec 2020 12:44:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D85D023331 for ; Tue, 22 Dec 2020 12:44:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726883AbgLVMnu (ORCPT ); Tue, 22 Dec 2020 07:43:50 -0500 Received: from out30-44.freemail.mail.aliyun.com ([115.124.30.44]:47483 "EHLO out30-44.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726644AbgLVMnu (ORCPT ); Tue, 22 Dec 2020 07:43:50 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R881e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04426;MF=weichen.chen@linux.alibaba.com;NM=1;PH=DS;RN=16;SR=0;TI=SMTPD_---0UJRQD2S_1608640950; Received: from localhost(mailfrom:weichen.chen@linux.alibaba.com fp:SMTPD_---0UJRQD2S_1608640950) by smtp.aliyun-inc.com(127.0.0.1); Tue, 22 Dec 2020 20:43:00 +0800 From: weichenchen Cc: splendidsky.cwc@alibaba-inc.com, yanxu.zw@alibaba-inc.com, weichenchen , "David S. Miller" , Jakub Kicinski , Alexey Kuznetsov , Hideaki YOSHIFUJI , Hangbin Liu , David Ahern , Jeff Dike , Roman Mashak , Nikolay Aleksandrov , Roopa Prabhu , Li RongQing , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v3] net: neighbor: fix a crash caused by mod zero Date: Tue, 22 Dec 2020 20:38:33 +0800 Message-Id: <20201222123838.12951-1-weichen.chen@linux.alibaba.com> X-Mailer: git-send-email 2.20.1 (Apple Git-117) In-Reply-To: <20201221113240.2ae38a77@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> References: <20201221113240.2ae38a77@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> MIME-Version: 1.0 To: unlisted-recipients:; (no To-header on input) 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 makes pneigh_enqueue() get a delay time passed in by the callers and the callers guarantee it is not zero. Signed-off-by: weichenchen --- V3: - Callers need to pass the delay time to pneigh_enqueue() now and they should guarantee it is not zero. - Use READ_ONCE() to read NEIGH_VAR(p, PROXY_DELAY) in both of the existing callers of pneigh_enqueue() and then pass it to pneigh_enqueue(). V2: - Use READ_ONCE() to prevent the complier from re-reading NEIGH_VAR(p, PROXY_DELAY). - Give a hint to the complier that delay <= 0 is unlikely to happen. --- include/net/neighbour.h | 2 +- net/core/neighbour.c | 5 ++--- net/ipv4/arp.c | 8 +++++--- net/ipv6/ndisc.c | 6 +++--- 4 files changed, 11 insertions(+), 10 deletions(-) diff --git a/include/net/neighbour.h b/include/net/neighbour.h index 22ced1381ede..f7564dc5304d 100644 --- a/include/net/neighbour.h +++ b/include/net/neighbour.h @@ -352,7 +352,7 @@ struct net *neigh_parms_net(const struct neigh_parms *parms) unsigned long neigh_rand_reach_time(unsigned long base); void pneigh_enqueue(struct neigh_table *tbl, struct neigh_parms *p, - struct sk_buff *skb); + struct sk_buff *skb, int delay); struct pneigh_entry *pneigh_lookup(struct neigh_table *tbl, struct net *net, const void *key, struct net_device *dev, int creat); diff --git a/net/core/neighbour.c b/net/core/neighbour.c index 9500d28a43b0..b440f966d109 100644 --- a/net/core/neighbour.c +++ b/net/core/neighbour.c @@ -1567,12 +1567,11 @@ static void neigh_proxy_process(struct timer_list *t) } void pneigh_enqueue(struct neigh_table *tbl, struct neigh_parms *p, - struct sk_buff *skb) + struct sk_buff *skb, int delay) { unsigned long now = jiffies; - unsigned long sched_next = now + (prandom_u32() % - NEIGH_VAR(p, PROXY_DELAY)); + unsigned long sched_next = now + (prandom_u32() % delay); if (tbl->proxy_queue.qlen > NEIGH_VAR(p, PROXY_QLEN)) { kfree_skb(skb); diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c index 922dd73e5740..6ddce6e0a648 100644 --- a/net/ipv4/arp.c +++ b/net/ipv4/arp.c @@ -841,20 +841,22 @@ static int arp_process(struct net *net, struct sock *sk, struct sk_buff *skb) arp_fwd_pvlan(in_dev, dev, rt, sip, tip) || (rt->dst.dev != dev && pneigh_lookup(&arp_tbl, net, &tip, dev, 0)))) { + int delay; + n = neigh_event_ns(&arp_tbl, sha, &sip, dev); if (n) neigh_release(n); + delay = READ_ONCE(NEIGH_VAR(in_dev->arp_parms, PROXY_DELAY)); if (NEIGH_CB(skb)->flags & LOCALLY_ENQUEUED || - skb->pkt_type == PACKET_HOST || - NEIGH_VAR(in_dev->arp_parms, PROXY_DELAY) == 0) { + skb->pkt_type == PACKET_HOST || delay == 0) { arp_send_dst(ARPOP_REPLY, ETH_P_ARP, sip, dev, tip, sha, dev->dev_addr, sha, reply_dst); } else { pneigh_enqueue(&arp_tbl, - in_dev->arp_parms, skb); + in_dev->arp_parms, skb, delay); goto out_free_dst; } goto out_consume_skb; diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c index 76717478f173..efdaaab47535 100644 --- a/net/ipv6/ndisc.c +++ b/net/ipv6/ndisc.c @@ -892,10 +892,10 @@ static void ndisc_recv_ns(struct sk_buff *skb) (idev->cnf.forwarding && (net->ipv6.devconf_all->proxy_ndp || idev->cnf.proxy_ndp) && (is_router = pndisc_is_router(&msg->target, dev)) >= 0)) { + int delay = READ_ONCE(NEIGH_VAR(idev->nd_parms, PROXY_DELAY)); if (!(NEIGH_CB(skb)->flags & LOCALLY_ENQUEUED) && skb->pkt_type != PACKET_HOST && - inc && - NEIGH_VAR(idev->nd_parms, PROXY_DELAY) != 0) { + inc && delay != 0) { /* * for anycast or proxy, * sender should delay its response @@ -905,7 +905,7 @@ static void ndisc_recv_ns(struct sk_buff *skb) */ struct sk_buff *n = skb_clone(skb, GFP_ATOMIC); if (n) - pneigh_enqueue(&nd_tbl, idev->nd_parms, n); + pneigh_enqueue(&nd_tbl, idev->nd_parms, n, delay); goto out; } } else