From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from m12-11.163.com (m12-11.163.com [220.181.12.11]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 7628572 for ; Thu, 10 Jun 2021 09:28:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=From:Subject:Message-ID:Date:MIME-Version; bh=V4U8V GIPScs250dEX3Ksv5D5Ie1IOyjuP6ltTQWgIAQ=; b=iENuMsemT5UV2WYkRwQsa D2xSOoe2cv4cyx9RGcV8MR+e9goYMGUMQS+MF056tiEoCAXbJ0yP57G60FXMq1yT 9CQsYCag29qg0YPY7JRc21tECyJWpK/y07fGYWuPsBoQB2w+wO3uSLak7SmJXIeZ a7YOSyp2MsSz7k+jcw+bns= Received: from [192.168.16.78] (unknown [110.86.5.93]) by smtp7 (Coremail) with SMTP id C8CowACHfIxA28FgMOz1hA--.24106S2; Thu, 10 Jun 2021 17:28:33 +0800 (CST) To: mptcp@lists.linux.dev Cc: Paolo Abeni From: Jianguo Wu Subject: [PATCH v2 1/4] mptcp: fix warning in __skb_flow_dissect() when do syn cookie for subflow join Message-ID: Date: Thu, 10 Jun 2021 17:28:32 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-CM-TRANSID:C8CowACHfIxA28FgMOz1hA--.24106S2 X-Coremail-Antispam: 1Uf129KBjvJXoWxuw43Jw1DWry3ZFW7Ar43ZFb_yoWxAr48pF 45GrZxGrWkJ3W3GF4SyFWUZrn09r4vkFW5K343Kwn2yFn8Wwn2vFy8Gr40vFy7KrW0k347 KFs7K3WkKFn7ZaDanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x07jEwZcUUUUU= X-Originating-IP: [110.86.5.93] X-CM-SenderInfo: 5zxmxt5qjx0iiqw6il2tof0z/1tbiUQGtkFWBTQ8RgAAAsq From: Jianguo Wu I got the following warning message while doing the test: [ 55.552626] TCP: request_sock_subflow: Possible SYN flooding on port 8099. Sending cookies. Check SNMP counters. [ 55.553024] ------------[ cut here ]------------ [ 55.553027] WARNING: CPU: 0 PID: 10 at net/core/flow_dissector.c:984 __skb_flow_dissect+0x280/0x1650 ... [ 55.553117] CPU: 0 PID: 10 Comm: ksoftirqd/0 Not tainted 5.12.0+ #18 [ 55.553121] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 02/27/2020 [ 55.553124] RIP: 0010:__skb_flow_dissect+0x280/0x1650 ... [ 55.553133] RSP: 0018:ffffb79580087770 EFLAGS: 00010246 [ 55.553137] RAX: 0000000000000000 RBX: ffffffff8ddb58e0 RCX: ffffb79580087888 [ 55.553139] RDX: ffffffff8ddb58e0 RSI: ffff8f7e4652b600 RDI: 0000000000000000 [ 55.553141] RBP: ffffb79580087858 R08: 0000000000000000 R09: 0000000000000008 [ 55.553143] R10: 000000008c622965 R11: 00000000d3313a5b R12: ffff8f7e4652b600 [ 55.553146] R13: ffff8f7e465c9062 R14: 0000000000000000 R15: ffffb79580087888 [ 55.553149] FS: 0000000000000000(0000) GS:ffff8f7f75e00000(0000) knlGS:0000000000000000 [ 55.553152] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 55.553154] CR2: 00007f73d1d19000 CR3: 0000000135e10004 CR4: 00000000003706f0 [ 55.553160] Call Trace: [ 55.553166] ? __sha256_final+0x67/0xd0 [ 55.553173] ? sha256+0x7e/0xa0 [ 55.553177] __skb_get_hash+0x57/0x210 [ 55.553182] subflow_init_req_cookie_join_save+0xac/0xc0 [ 55.553189] subflow_check_req+0x474/0x550 [ 55.553195] ? ip_route_output_key_hash+0x67/0x90 [ 55.553200] ? xfrm_lookup_route+0x1d/0xa0 [ 55.553207] subflow_v4_route_req+0x8e/0xd0 [ 55.553212] tcp_conn_request+0x31e/0xab0 [ 55.553218] ? selinux_socket_sock_rcv_skb+0x116/0x210 [ 55.553224] ? tcp_rcv_state_process+0x179/0x6d0 [ 55.553229] tcp_rcv_state_process+0x179/0x6d0 [ 55.553235] tcp_v4_do_rcv+0xaf/0x220 [ 55.553239] tcp_v4_rcv+0xce4/0xd80 [ 55.553243] ? ip_route_input_rcu+0x246/0x260 [ 55.553248] ip_protocol_deliver_rcu+0x35/0x1b0 [ 55.553253] ip_local_deliver_finish+0x44/0x50 [ 55.553258] ip_local_deliver+0x6c/0x110 [ 55.553262] ? ip_rcv_finish_core.isra.19+0x5a/0x400 [ 55.553267] ip_rcv+0xd1/0xe0 ... After debugging, I found in __skb_flow_dissect(), skb->dev and skb->sk are both NULL, then net is NULL, and trigger WARN_ON_ONCE(!net), actually net is always NULL in this code path, as skb->dev is set to NULL in tcp_v4_rcv(), and skb->sk is never set. Code snippet in __skb_flow_dissect() that trigger warning: 975 if (skb) { 976 if (!net) { 977 if (skb->dev) 978 net = dev_net(skb->dev); 979 else if (skb->sk) 980 net = sock_net(skb->sk); 981 } 982 } 983 984 WARN_ON_ONCE(!net); So, use 4-tuple derived hash. Fixes: 9466a1ccebbe("mptcp: enable JOIN requests even if cookies are in use"). Suggested-by: Paolo Abeni Signed-off-by: Jianguo Wu --- net/mptcp/syncookies.c | 57 ++++++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 53 insertions(+), 4 deletions(-) diff --git a/net/mptcp/syncookies.c b/net/mptcp/syncookies.c index abe0fd0..11721b3 100644 --- a/net/mptcp/syncookies.c +++ b/net/mptcp/syncookies.c @@ -35,13 +35,62 @@ struct join_entry { static struct join_entry join_entries[COOKIE_JOIN_SLOTS] __cacheline_aligned_in_smp; static spinlock_t join_entry_locks[COOKIE_JOIN_SLOTS] __cacheline_aligned_in_smp; -static u32 mptcp_join_entry_hash(struct sk_buff *skb, struct net *net) +static u32 mptcp_join_hashfn(const struct net *net, const __be32 laddr, + const __be16 lport, const __be32 faddr, + const __be16 fport) { - u32 i = skb_get_hash(skb) ^ net_hash_mix(net); + static u32 mptcp_join_hash_secret __read_mostly; + u32 i; + + net_get_random_once(&mptcp_join_hash_secret, + sizeof(mptcp_join_hash_secret)); + + i = jhash_3words((__force __u32) laddr, + (__force __u32) faddr, + ((__u32) lport) << 16 | (__force __u32)fport, + mptcp_join_hash_secret + net_hash_mix(net)); + + return i % ARRAY_SIZE(join_entries); +} + +static u32 mptcp_join_hashfn_inet6(const struct net *net, + const struct in6_addr *laddr, const u16 lport, + const struct in6_addr *faddr, const __be16 fport) +{ + static u32 mptcp_join_hash_secret_v6 __read_mostly; + static u32 ipv6_hash_secret __read_mostly; + u32 lhash, fhash, ports, i; + + net_get_random_once(&mptcp_join_hash_secret_v6, + sizeof(mptcp_join_hash_secret_v6)); + net_get_random_once(&ipv6_hash_secret, sizeof(ipv6_hash_secret)); + + lhash = (__force u32)laddr->s6_addr32[3]; + fhash = __ipv6_addr_jhash(faddr, ipv6_hash_secret); + ports = (((u32)lport) << 16) | (__force u32)fport; + + i = jhash_3words(lhash, fhash, ports, + mptcp_join_hash_secret_v6 + net_hash_mix(net)); return i % ARRAY_SIZE(join_entries); } +static u32 mptcp_join_entry_hash(struct sk_buff *skb, struct net *net, + unsigned short family) +{ + struct tcphdr *th = tcp_hdr(skb); + +#if IS_ENABLED(CONFIG_IPV6) + if (family == AF_INET6 && + !ipv6_addr_v4mapped(&ipv6_hdr(skb)->saddr)) + return mptcp_join_hashfn_inet6(net, + &ipv6_hdr(skb)->daddr, th->dest, + &ipv6_hdr(skb)->saddr, th->source); +#endif + return mptcp_join_hashfn(net, ip_hdr(skb)->daddr, th->dest, + ip_hdr(skb)->saddr, th->source); +} + static void mptcp_join_store_state(struct join_entry *entry, const struct mptcp_subflow_request_sock *subflow_req) { @@ -58,7 +107,7 @@ void subflow_init_req_cookie_join_save(const struct mptcp_subflow_request_sock * struct sk_buff *skb) { struct net *net = read_pnet(&subflow_req->sk.req.ireq_net); - u32 i = mptcp_join_entry_hash(skb, net); + u32 i = mptcp_join_entry_hash(skb, net, subflow_req->sk.req.ireq_family); /* No use in waiting if other cpu is already using this slot -- * would overwrite the data that got stored. @@ -79,7 +128,7 @@ bool mptcp_token_join_cookie_init_state(struct mptcp_subflow_request_sock *subfl struct sk_buff *skb) { struct net *net = read_pnet(&subflow_req->sk.req.ireq_net); - u32 i = mptcp_join_entry_hash(skb, net); + u32 i = mptcp_join_entry_hash(skb, net, subflow_req->sk.req.ireq_family); struct mptcp_sock *msk; struct join_entry *e; -- 1.8.3.1