From patchwork Wed Jun 9 10:39:44 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jianguo Wu X-Patchwork-Id: 12309629 X-Patchwork-Delegate: pabeni@redhat.com Received: from m12-12.163.com (m12-12.163.com [220.181.12.12]) by smtp.subspace.kernel.org (Postfix) with ESMTP id E35EB72 for ; Wed, 9 Jun 2021 10:55:36 +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=TtCAT c3+hDznOkCqIE1naNCgakUzmlxoOCNxzSaHqSw=; b=hE10Y375dmxpRCaNwJgDO syzjmuxcKyVnW4DkTEFG3rzq9Cyl0GbVn5BZbXUoCN3pavgMIWFeZN4AXoi/T+MM KE9xvVKpPntj/2XvXqwgZ9tJnnE2uAAmR0EhXDgr65HUi74JLQ0ZWaXvTx+HaVnc 4rMkSEFDrzR/qn/KoM7t/g= Received: from [192.168.16.78] (unknown [110.80.1.45]) by smtp8 (Coremail) with SMTP id DMCowAAXDPhvmsBgIjexIw--.39002S2; Wed, 09 Jun 2021 18:39:45 +0800 (CST) From: Jianguo Wu Subject: [PATCH 1/3] mptcp: fix warning in __skb_flow_dissect() when do syn cookie for subflow join To: mptcp@lists.linux.dev Cc: Paolo Abeni , Florian Westphal Message-ID: Date: Wed, 9 Jun 2021 18:39:44 +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 X-CM-TRANSID: DMCowAAXDPhvmsBgIjexIw--.39002S2 X-Coremail-Antispam: 1Uf129KBjvJXoWxAw4DCrWfZFy3AFy7Gr17KFg_yoWruw47pF 45GrZxGrWkJwn8Jr4YyrW7Xrn0gw4qvFWkKw1Syrn2y3Z8Gwn2qFy8Jr40vFy7GrWjk347 KFnrG3W8KFn7ZaUanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x07j_PEfUUUUU= X-Originating-IP: [110.80.1.45] X-CM-SenderInfo: 5zxmxt5qjx0iiqw6il2tof0z/1tbiNxGskFWBkvqRFQAAsi 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, if the skb->hash is not available, then fallback to 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 | 24 +++++++++++++++++++++++- 1 file changed, 23 insertions(+), 1 deletion(-) diff --git a/net/mptcp/syncookies.c b/net/mptcp/syncookies.c index abe0fd0..778bdba 100644 --- a/net/mptcp/syncookies.c +++ b/net/mptcp/syncookies.c @@ -35,9 +35,31 @@ 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_hashfn(const struct net *net, const __be32 laddr, + const __be16 lport, const __be32 faddr, + const __be16 fport) +{ + static u32 mptcp_join_hash_secret __read_mostly; + + net_get_random_once(&mptcp_join_hash_secret, sizeof(mptcp_join_hash_secret)); + + return jhash_3words((__force __u32) laddr, + (__force __u32) faddr, + ((__u32) lport) << 16 | (__force __u32)fport, + mptcp_join_hash_secret + net_hash_mix(net)); +} + static u32 mptcp_join_entry_hash(struct sk_buff *skb, struct net *net) { - u32 i = skb_get_hash(skb) ^ net_hash_mix(net); + u32 i; + struct iphdr *iph = ip_hdr(skb); + struct tcphdr *th = tcp_hdr(skb); + + if (!skb_get_hash_raw(skb)) + i = mptcp_join_hashfn(net, iph->daddr, th->dest, + iph->saddr, th->source); + else + i = skb_get_hash_raw(skb) ^ net_hash_mix(net); return i % ARRAY_SIZE(join_entries); }