* [PATCH] mptcp: fix warning in __skb_flow_dissect() when do syn cookie for subflow join
@ 2021-06-05 3:24 Jianguo Wu
2021-06-07 11:07 ` Paolo Abeni
0 siblings, 1 reply; 3+ messages in thread
From: Jianguo Wu @ 2021-06-05 3:24 UTC (permalink / raw)
To: mptcp; +Cc: Florian Westphal
From: Jianguo Wu <wujianguo@chinatelecom.cn>
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.
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);
skb->dev is set to NULL in tcp_v4_rcv(), and skb->sk is never set in this code path.
But for sk_state is TCP_NEW_SYN_RECV or TCP_TIME_WAIT, skb->dev is not set to NULL,
so we can remove skb->dev = NULL in tcp_v4_rcv()?
Fixes: 9466a1ccebbe("mptcp: enable JOIN requests even if cookies are in use").
---
net/ipv4/tcp_ipv4.c | 2 --
1 file changed, 2 deletions(-)
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 4f5b68a..b1f94a4 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2061,8 +2061,6 @@ int tcp_v4_rcv(struct sk_buff *skb)
iph = ip_hdr(skb);
tcp_v4_fill_cb(skb, iph, th);
- skb->dev = NULL;
-
if (sk->sk_state == TCP_LISTEN) {
ret = tcp_v4_do_rcv(sk, skb);
goto put_and_return;
--
1.8.3.1
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] mptcp: fix warning in __skb_flow_dissect() when do syn cookie for subflow join
2021-06-05 3:24 [PATCH] mptcp: fix warning in __skb_flow_dissect() when do syn cookie for subflow join Jianguo Wu
@ 2021-06-07 11:07 ` Paolo Abeni
2021-06-08 1:15 ` Jianguo Wu
0 siblings, 1 reply; 3+ messages in thread
From: Paolo Abeni @ 2021-06-07 11:07 UTC (permalink / raw)
To: Jianguo Wu, mptcp; +Cc: Florian Westphal
Hello,
On Sat, 2021-06-05 at 11:24 +0800, Jianguo Wu wrote:
> From: Jianguo Wu <wujianguo@chinatelecom.cn>
>
> 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.
>
> 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);
>
> skb->dev is set to NULL in tcp_v4_rcv(), and skb->sk is never set in this code path.
> But for sk_state is TCP_NEW_SYN_RECV or TCP_TIME_WAIT, skb->dev is not set to NULL,
> so we can remove skb->dev = NULL in tcp_v4_rcv()?
Thank you for the detailed report!
I'm unable to find easily any negative side effect to remove such
assignment, still I'm more than a bit uneasy for such change.
The issue is clearly an mptcp-specific one, so I think event the fix
should be mptcp-specific.
If the skb->hash is not available - !skb_get_hash_raw(skb) == 0, then
we could fallback using an sk-derived hash, e.g. doing something alike
what inet_ehashfn() does - with different seeds/secrets.
Cheers,
Paolo
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] mptcp: fix warning in __skb_flow_dissect() when do syn cookie for subflow join
2021-06-07 11:07 ` Paolo Abeni
@ 2021-06-08 1:15 ` Jianguo Wu
0 siblings, 0 replies; 3+ messages in thread
From: Jianguo Wu @ 2021-06-08 1:15 UTC (permalink / raw)
To: Paolo Abeni, mptcp; +Cc: Florian Westphal
Hi Paolo,
On 2021/6/7 19:07, Paolo Abeni wrote:
> Hello,
>
> On Sat, 2021-06-05 at 11:24 +0800, Jianguo Wu wrote:
>> From: Jianguo Wu <wujianguo@chinatelecom.cn>
>>
>> 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.
>>
>> 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);
>>
>> skb->dev is set to NULL in tcp_v4_rcv(), and skb->sk is never set in this code path.
>> But for sk_state is TCP_NEW_SYN_RECV or TCP_TIME_WAIT, skb->dev is not set to NULL,
>> so we can remove skb->dev = NULL in tcp_v4_rcv()?
>
> Thank you for the detailed report!
>
> I'm unable to find easily any negative side effect to remove such
> assignment, still I'm more than a bit uneasy for such change.
>
> The issue is clearly an mptcp-specific one, so I think event the fix
> should be mptcp-specific.
>
> If the skb->hash is not available - !skb_get_hash_raw(skb) == 0, then
> we could fallback using an sk-derived hash, e.g. doing something alike
> what inet_ehashfn() does - with different seeds/secrets.
>
I will try to prepare a new patch as your suggestion, Thanks!
> Cheers,
>
> Paolo
>
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2021-06-08 1:16 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2021-06-05 3:24 [PATCH] mptcp: fix warning in __skb_flow_dissect() when do syn cookie for subflow join Jianguo Wu
2021-06-07 11:07 ` Paolo Abeni
2021-06-08 1:15 ` Jianguo Wu
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