From nobody Mon Dec 15 23:14:02 2025 Delivered-To: importer2@patchew.org Received-SPF: pass (zohomail.com: domain of vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; envelope-from=linux-kernel-owner@vger.kernel.org; helo=vger.kernel.org; Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail(p=none dis=none) header.from=linux.alibaba.com ARC-Seal: i=1; a=rsa-sha256; t=1608641069; cv=none; d=zohomail.com; s=zohoarc; b=a9iP+QevjS/8zy3dEBj9yGE9krJxDo0RkRzYC5o6MDcNFl/CMr4NKZlZcGOxngGMzDsprWPSwrKfdaTBirlk2PJ53CDZV8kzwwzNTxigAguaBNFfN+rMO60NThNS0kWpPfYs0p+t8Aozp8utO/204DZbxz49uD6/QvlS0KXEVnI= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1608641069; h=Content-Transfer-Encoding:Cc:Date:From:In-Reply-To:List-Id:MIME-Version:Message-ID:References:Subject:To; bh=e5fOifep5recxgnyfyKyWBMNFH2FudmoMoHDgSGQLps=; b=AgKCtNkXJvjXLRKEkZK3IZoy0sF7C6gA83Evd0+VsnlxGYFvRQPJQwFMkQU963hNlANO8k/EMfduFbq8lT8OihvfwocCNh36zCQffhrixWIwqsiZ9f1aOFHtY6i2MelS6q5g8mJ9y5Bgt/shWork0V1DZ0Y4Y8Ecs4VTtEpxQe4= ARC-Authentication-Results: i=1; mx.zohomail.com; spf=pass (zohomail.com: domain of vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail header.from= (p=none dis=none) header.from= Return-Path: Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mx.zohomail.com with SMTP id 1608641069196657.0706888945771; Tue, 22 Dec 2020 04:44:29 -0800 (PST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726903AbgLVMnu (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 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 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; 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 Content-Transfer-Encoding: quoted-printable To: unlisted-recipients:; (no To-header on input) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" 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 <=3D 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 *p= arms) unsigned long neigh_rand_reach_time(unsigned long base); =20 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 *ne= t, 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) } =20 void pneigh_enqueue(struct neigh_table *tbl, struct neigh_parms *p, - struct sk_buff *skb) + struct sk_buff *skb, int delay) { unsigned long now =3D jiffies; =20 - unsigned long sched_next =3D now + (prandom_u32() % - NEIGH_VAR(p, PROXY_DELAY)); + unsigned long sched_next =3D now + (prandom_u32() % delay); =20 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 !=3D dev && pneigh_lookup(&arp_tbl, net, &tip, dev, 0)))) { + int delay; + n =3D neigh_event_ns(&arp_tbl, sha, &sip, dev); if (n) neigh_release(n); =20 + delay =3D READ_ONCE(NEIGH_VAR(in_dev->arp_parms, PROXY_DELAY)); if (NEIGH_CB(skb)->flags & LOCALLY_ENQUEUED || - skb->pkt_type =3D=3D PACKET_HOST || - NEIGH_VAR(in_dev->arp_parms, PROXY_DELAY) =3D=3D 0) { + skb->pkt_type =3D=3D PACKET_HOST || delay =3D=3D 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 =3D pndisc_is_router(&msg->target, dev)) >=3D 0)) { + int delay =3D READ_ONCE(NEIGH_VAR(idev->nd_parms, PROXY_DELAY)); if (!(NEIGH_CB(skb)->flags & LOCALLY_ENQUEUED) && skb->pkt_type !=3D PACKET_HOST && - inc && - NEIGH_VAR(idev->nd_parms, PROXY_DELAY) !=3D 0) { + inc && delay !=3D 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 =3D 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 --=20 2.20.1 (Apple Git-117)