From patchwork Sat Jul 23 11:02:02 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Pablo Neira Ayuso X-Patchwork-Id: 651873 X-Patchwork-Delegate: pablo@netfilter.org Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 3rxPkS6Cwmz9t1V for ; Sat, 23 Jul 2016 21:02:56 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751137AbcGWLC4 (ORCPT ); Sat, 23 Jul 2016 07:02:56 -0400 Received: from mail.us.es ([193.147.175.20]:35230 "EHLO mail.us.es" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751082AbcGWLCz (ORCPT ); Sat, 23 Jul 2016 07:02:55 -0400 Received: from antivirus1-rhel7.int (unknown [192.168.2.11]) by mail.us.es (Postfix) with ESMTP id E8988E7DAA for ; Sat, 23 Jul 2016 13:02:53 +0200 (CEST) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id D67FCFC618 for ; Sat, 23 Jul 2016 13:02:53 +0200 (CEST) Received: by antivirus1-rhel7.int (Postfix, from userid 99) id CBBFFFB469; Sat, 23 Jul 2016 13:02:53 +0200 (CEST) X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on antivirus1-rhel7.int X-Spam-Level: X-Spam-Status: No, score=-103.0 required=7.5 tests=BAYES_50,RDNS_DYNAMIC, SMTPAUTH_US,USER_IN_WHITELIST autolearn=disabled version=3.4.1 Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id 03494FAB56 for ; Sat, 23 Jul 2016 13:02:51 +0200 (CEST) Received: from 192.168.1.13 (192.168.1.13) by antivirus1-rhel7.int (F-Secure/fsigk_smtp/530/antivirus1-rhel7.int); Sat, 23 Jul 2016 13:02:51 +0200 (CEST) X-Virus-Status: clean(F-Secure/fsigk_smtp/530/antivirus1-rhel7.int) Received: (qmail 20473 invoked from network); 23 Jul 2016 13:02:50 +0200 Received: from 142.235.137.78.rev.vodafone.pt (HELO salvia.VodafoneMobile.wifi) (pneira@us.es@78.137.235.142) by mail.us.es with SMTP; 23 Jul 2016 13:02:50 +0200 From: Pablo Neira Ayuso To: netfilter-devel@vger.kernel.org Cc: davem@davemloft.net Subject: [PATCH 02/25] netfilter: conntrack: fix race between nf_conntrack proc read and hash resize Date: Sat, 23 Jul 2016 13:02:02 +0200 Message-Id: <1469271745-14523-3-git-send-email-pablo@netfilter.org> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1469271745-14523-1-git-send-email-pablo@netfilter.org> References: <1469271745-14523-1-git-send-email-pablo@netfilter.org> MIME-Version: 1.0 X-Virus-Scanned: ClamAV using ClamSMTP Sender: netfilter-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org From: Liping Zhang When we do "cat /proc/net/nf_conntrack", and meanwhile resize the conntrack hash table via /sys/module/nf_conntrack/parameters/hashsize, race will happen, because reader can observe a newly allocated hash but the old size (or vice versa). So oops will happen like follows： BUG: unable to handle kernel NULL pointer dereference at 0000000000000017 IP: [] seq_print_acct+0x11/0x50 [nf_conntrack] Call Trace: [] ? ct_seq_show+0x14e/0x340 [nf_conntrack] [] seq_read+0x2cc/0x390 [] proc_reg_read+0x42/0x70 [] __vfs_read+0x37/0x130 [] ? security_file_permission+0xa0/0xc0 [] vfs_read+0x95/0x140 [] SyS_read+0x55/0xc0 [] entry_SYSCALL_64_fastpath+0x1a/0xa4 It is very easy to reproduce this kernel crash. 1. open one shell and input the following cmds: while : ; do echo $RANDOM > /sys/module/nf_conntrack/parameters/hashsize done 2. open more shells and input the following cmds: while : ; do cat /proc/net/nf_conntrack done 3. just wait a monent, oops will happen soon. The solution in this patch is based on Florian's Commit 5e3c61f98175 ("netfilter: conntrack: fix lookup race during hash resize"). And add a wrapper function nf_conntrack_get_ht to get hash and hsize suggested by Florian Westphal. Signed-off-by: Liping Zhang Signed-off-by: Pablo Neira Ayuso --- include/net/netfilter/nf_conntrack_core.h | 2 ++ net/ipv4/netfilter/nf_conntrack_l3proto_ipv4_compat.c | 14 ++++++++++---- net/netfilter/nf_conntrack_core.c | 17 +++++++++++++++++ net/netfilter/nf_conntrack_standalone.c | 14 +++++++++----- 4 files changed, 38 insertions(+), 9 deletions(-) diff --git a/include/net/netfilter/nf_conntrack_core.h b/include/net/netfilter/nf_conntrack_core.h index 3e2f332..79d7ac5 100644 --- a/include/net/netfilter/nf_conntrack_core.h +++ b/include/net/netfilter/nf_conntrack_core.h @@ -51,6 +51,8 @@ bool nf_ct_invert_tuple(struct nf_conntrack_tuple *inverse, const struct nf_conntrack_l3proto *l3proto, const struct nf_conntrack_l4proto *l4proto); +void nf_conntrack_get_ht(struct hlist_nulls_head **hash, unsigned int *hsize); + /* Find a connection corresponding to a tuple. */ struct nf_conntrack_tuple_hash * nf_conntrack_find_get(struct net *net, diff --git a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4_compat.c b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4_compat.c index c6f3c40..6392371 100644 --- a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4_compat.c +++ b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4_compat.c @@ -26,6 +26,8 @@ struct ct_iter_state { struct seq_net_private p; + struct hlist_nulls_head *hash; + unsigned int htable_size; unsigned int bucket; }; @@ -35,10 +37,10 @@ static struct hlist_nulls_node *ct_get_first(struct seq_file *seq) struct hlist_nulls_node *n; for (st->bucket = 0; - st->bucket < nf_conntrack_htable_size; + st->bucket < st->htable_size; st->bucket++) { n = rcu_dereference( - hlist_nulls_first_rcu(&nf_conntrack_hash[st->bucket])); + hlist_nulls_first_rcu(&st->hash[st->bucket])); if (!is_a_nulls(n)) return n; } @@ -53,11 +55,11 @@ static struct hlist_nulls_node *ct_get_next(struct seq_file *seq, head = rcu_dereference(hlist_nulls_next_rcu(head)); while (is_a_nulls(head)) { if (likely(get_nulls_value(head) == st->bucket)) { - if (++st->bucket >= nf_conntrack_htable_size) + if (++st->bucket >= st->htable_size) return NULL; } head = rcu_dereference( - hlist_nulls_first_rcu(&nf_conntrack_hash[st->bucket])); + hlist_nulls_first_rcu(&st->hash[st->bucket])); } return head; } @@ -75,7 +77,11 @@ static struct hlist_nulls_node *ct_get_idx(struct seq_file *seq, loff_t pos) static void *ct_seq_start(struct seq_file *seq, loff_t *pos) __acquires(RCU) { + struct ct_iter_state *st = seq->private; + rcu_read_lock(); + + nf_conntrack_get_ht(&st->hash, &st->htable_size); return ct_get_idx(seq, *pos); } diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c index 153e33f..1289e7e 100644 --- a/net/netfilter/nf_conntrack_core.c +++ b/net/netfilter/nf_conntrack_core.c @@ -460,6 +460,23 @@ nf_ct_key_equal(struct nf_conntrack_tuple_hash *h, net_eq(net, nf_ct_net(ct)); } +/* must be called with rcu read lock held */ +void nf_conntrack_get_ht(struct hlist_nulls_head **hash, unsigned int *hsize) +{ + struct hlist_nulls_head *hptr; + unsigned int sequence, hsz; + + do { + sequence = read_seqcount_begin(&nf_conntrack_generation); + hsz = nf_conntrack_htable_size; + hptr = nf_conntrack_hash; + } while (read_seqcount_retry(&nf_conntrack_generation, sequence)); + + *hash = hptr; + *hsize = hsz; +} +EXPORT_SYMBOL_GPL(nf_conntrack_get_ht); + /* * Warning : * - Caller must take a reference on returned object diff --git a/net/netfilter/nf_conntrack_standalone.c b/net/netfilter/nf_conntrack_standalone.c index 2aaa188..958a145 100644 --- a/net/netfilter/nf_conntrack_standalone.c +++ b/net/netfilter/nf_conntrack_standalone.c @@ -48,6 +48,8 @@ EXPORT_SYMBOL_GPL(print_tuple); struct ct_iter_state { struct seq_net_private p; + struct hlist_nulls_head *hash; + unsigned int htable_size; unsigned int bucket; u_int64_t time_now; }; @@ -58,9 +60,10 @@ static struct hlist_nulls_node *ct_get_first(struct seq_file *seq) struct hlist_nulls_node *n; for (st->bucket = 0; - st->bucket < nf_conntrack_htable_size; + st->bucket < st->htable_size; st->bucket++) { - n = rcu_dereference(hlist_nulls_first_rcu(&nf_conntrack_hash[st->bucket])); + n = rcu_dereference( + hlist_nulls_first_rcu(&st->hash[st->bucket])); if (!is_a_nulls(n)) return n; } @@ -75,12 +78,11 @@ static struct hlist_nulls_node *ct_get_next(struct seq_file *seq, head = rcu_dereference(hlist_nulls_next_rcu(head)); while (is_a_nulls(head)) { if (likely(get_nulls_value(head) == st->bucket)) { - if (++st->bucket >= nf_conntrack_htable_size) + if (++st->bucket >= st->htable_size) return NULL; } head = rcu_dereference( - hlist_nulls_first_rcu( - &nf_conntrack_hash[st->bucket])); + hlist_nulls_first_rcu(&st->hash[st->bucket])); } return head; } @@ -102,6 +104,8 @@ static void *ct_seq_start(struct seq_file *seq, loff_t *pos) st->time_now = ktime_get_real_ns(); rcu_read_lock(); + + nf_conntrack_get_ht(&st->hash, &st->htable_size); return ct_get_idx(seq, *pos); }