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=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 E71BDC28CC0 for ; Wed, 29 May 2019 10:25:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BDB362070D for ; Wed, 29 May 2019 10:25:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726909AbfE2KZt (ORCPT ); Wed, 29 May 2019 06:25:49 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:40604 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726687AbfE2KZp (ORCPT ); Wed, 29 May 2019 06:25:45 -0400 Received: from 1.general.smb.uk.vpn ([10.172.193.28] helo=canonical.com) by youngberry.canonical.com with esmtpsa (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.76) (envelope-from ) id 1hVvmB-0003im-KS; Wed, 29 May 2019 10:25:43 +0000 From: Stefan Bader To: stable , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Eric Dumazet , Sasha Levin , Peter Oskolkov , Ben Hutchings , Andy Whitcroft , Greg KH Subject: [PATCH 1/4] ipv4: ipv6: netfilter: Adjust the frag mem limit when truesize changes Date: Wed, 29 May 2019 12:25:39 +0200 Message-Id: <20190529102542.17742-2-stefan.bader@canonical.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190529102542.17742-1-stefan.bader@canonical.com> References: <20190529102542.17742-1-stefan.bader@canonical.com> Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Jiri Wiesner The *_frag_reasm() functions are susceptible to miscalculating the byte count of packet fragments in case the truesize of a head buffer changes. The truesize member may be changed by the call to skb_unclone(), leaving the fragment memory limit counter unbalanced even if all fragments are processed. This miscalculation goes unnoticed as long as the network namespace which holds the counter is not destroyed. Should an attempt be made to destroy a network namespace that holds an unbalanced fragment memory limit counter the cleanup of the namespace never finishes. The thread handling the cleanup gets stuck in inet_frags_exit_net() waiting for the percpu counter to reach zero. The thread is usually in running state with a stacktrace similar to: PID: 1073 TASK: ffff880626711440 CPU: 1 COMMAND: "kworker/u48:4" #5 [ffff880621563d48] _raw_spin_lock at ffffffff815f5480 #6 [ffff880621563d48] inet_evict_bucket at ffffffff8158020b #7 [ffff880621563d80] inet_frags_exit_net at ffffffff8158051c #8 [ffff880621563db0] ops_exit_list at ffffffff814f5856 #9 [ffff880621563dd8] cleanup_net at ffffffff814f67c0 #10 [ffff880621563e38] process_one_work at ffffffff81096f14 It is not possible to create new network namespaces, and processes that call unshare() end up being stuck in uninterruptible sleep state waiting to acquire the net_mutex. The bug was observed in the IPv6 netfilter code by Per Sundstrom. I thank him for his analysis of the problem. The parts of this patch that apply to IPv4 and IPv6 fragment reassembly are preemptive measures. Signed-off-by: Jiri Wiesner Reported-by: Per Sundstrom Acked-by: Peter Oskolkov Signed-off-by: David S. Miller (backported from commit ebaf39e6032faf77218220707fc3fa22487784e0) [smb: context adjustments in net/ipv6/netfilter/nf_conntrack_reasm.c] Signed-off-by: Stefan Bader --- net/ipv4/ip_fragment.c | 7 +++++++ net/ipv6/netfilter/nf_conntrack_reasm.c | 8 +++++++- net/ipv6/reassembly.c | 8 +++++++- 3 files changed, 21 insertions(+), 2 deletions(-) diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c index 2c75330b1c71..5387e6ab78d7 100644 --- a/net/ipv4/ip_fragment.c +++ b/net/ipv4/ip_fragment.c @@ -519,6 +519,7 @@ static int ip_frag_reasm(struct ipq *qp, struct sk_buff *skb, struct rb_node *rbn; int len; int ihlen; + int delta; int err; u8 ecn; @@ -560,10 +561,16 @@ static int ip_frag_reasm(struct ipq *qp, struct sk_buff *skb, if (len > 65535) goto out_oversize; + delta = - head->truesize; + /* Head of list must not be cloned. */ if (skb_unclone(head, GFP_ATOMIC)) goto out_nomem; + delta += head->truesize; + if (delta) + add_frag_mem_limit(qp->q.net, delta); + /* If the first fragment is fragmented itself, we split * it to two chunks: the first with data and paged part * and the second, holding only fragments. */ diff --git a/net/ipv6/netfilter/nf_conntrack_reasm.c b/net/ipv6/netfilter/nf_conntrack_reasm.c index 664c84e47bab..e5d06ceb2c0c 100644 --- a/net/ipv6/netfilter/nf_conntrack_reasm.c +++ b/net/ipv6/netfilter/nf_conntrack_reasm.c @@ -353,7 +353,7 @@ static struct sk_buff * nf_ct_frag6_reasm(struct frag_queue *fq, struct net_device *dev) { struct sk_buff *fp, *op, *head = fq->q.fragments; - int payload_len; + int payload_len, delta; u8 ecn; inet_frag_kill(&fq->q); @@ -374,12 +374,18 @@ nf_ct_frag6_reasm(struct frag_queue *fq, struct net_device *dev) goto out_oversize; } + delta = - head->truesize; + /* Head of list must not be cloned. */ if (skb_unclone(head, GFP_ATOMIC)) { pr_debug("skb is cloned but can't expand head"); goto out_oom; } + delta += head->truesize; + if (delta) + add_frag_mem_limit(fq->q.net, delta); + /* If the first fragment is fragmented itself, we split * it to two chunks: the first with data and paged part * and the second, holding only fragments. */ diff --git a/net/ipv6/reassembly.c b/net/ipv6/reassembly.c index ec917f58d105..020cf70273c9 100644 --- a/net/ipv6/reassembly.c +++ b/net/ipv6/reassembly.c @@ -343,7 +343,7 @@ static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *prev, { struct net *net = container_of(fq->q.net, struct net, ipv6.frags); struct sk_buff *fp, *head = fq->q.fragments; - int payload_len; + int payload_len, delta; unsigned int nhoff; int sum_truesize; u8 ecn; @@ -384,10 +384,16 @@ static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *prev, if (payload_len > IPV6_MAXPLEN) goto out_oversize; + delta = - head->truesize; + /* Head of list must not be cloned. */ if (skb_unclone(head, GFP_ATOMIC)) goto out_oom; + delta += head->truesize; + if (delta) + add_frag_mem_limit(fq->q.net, delta); + /* If the first fragment is fragmented itself, we split * it to two chunks: the first with data and paged part * and the second, holding only fragments. */ -- 2.17.1