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Date:	Fri, 30 Oct 2015 19:38:08 +0000
From:	Haiyang Zhang <haiyangz@...rosoft.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	"edumazet@...gle.com" <edumazet@...gle.com>,
	David Miller <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"KY Srinivasan" <kys@...rosoft.com>
Subject: RE: [patch] tcp: attach SYNACK messages to request sockets instead of
 listener



> -----Original Message-----
> From: Eric Dumazet [mailto:eric.dumazet@...il.com]
> Sent: Thursday, October 29, 2015 6:59 PM
> To: Haiyang Zhang <haiyangz@...rosoft.com>
> Cc: edumazet@...gle.com; David Miller <davem@...emloft.net>;
> netdev@...r.kernel.org; KY Srinivasan <kys@...rosoft.com>
> Subject: Re: [patch] tcp: attach SYNACK messages to request sockets
> instead of listener
> 
> 
> Thanks for this report.
> 
> Somehow I knew such bugs would surface ;)
> 
> Please try following debugging patch ?
> 
> We need to identify which part of the kernel is messed up.
> 
> diff --git a/include/net/sock.h b/include/net/sock.h
> index aeed5c95f3ca..a643499d37e2 100644
> --- a/include/net/sock.h
> +++ b/include/net/sock.h
> @@ -1951,6 +1951,14 @@ static inline void skb_set_hash_from_sk(struct
> sk_buff *skb, struct sock *sk)
>  	}
>  }
> 
> +/* This helper checks if a socket is a full socket,
> + * ie _not_ a timewait or request socket.
> + */
> +static inline bool sk_fullsock(const struct sock *sk)
> +{
> +	return (1 << sk->sk_state) & ~(TCPF_TIME_WAIT | TCPF_NEW_SYN_RECV);
> +}
> +
>  /*
>   *	Queue a received datagram if it will fit. Stream and sequenced
>   *	protocols can't normally use this as they need to fit buffers in
> @@ -1962,6 +1970,10 @@ static inline void skb_set_hash_from_sk(struct
> sk_buff *skb, struct sock *sk)
> 
>  static inline void skb_set_owner_w(struct sk_buff *skb, struct sock *sk)
>  {
> +	if (!sk_fullsock(sk)) {
> +		WARN_ON_ONCE(1);
> +		return;
> +	}
>  	skb_orphan(skb);
>  	skb->sk = sk;
>  	skb->destructor = sock_wfree;
> @@ -2223,14 +2235,6 @@ static inline struct sock *skb_steal_sock(struct
> sk_buff *skb)
>  	return NULL;
>  }
> 
> -/* This helper checks if a socket is a full socket,
> - * ie _not_ a timewait or request socket.
> - */
> -static inline bool sk_fullsock(const struct sock *sk)
> -{
> -	return (1 << sk->sk_state) & ~(TCPF_TIME_WAIT | TCPF_NEW_SYN_RECV);
> -}
> -
>  /* This helper checks if a socket is a LISTEN or NEW_SYN_RECV
>   * SYNACK messages can be attached to either ones (depending on
> SYNCOOKIE)
>   */
> 

Hi Eric,

Thanks for the debug patch. The panic does not happen anymore with
the patch. I see a warning call trace:

[  222.307948] ------------[ cut here ]------------
[  222.308009] WARNING: CPU: 6 PID: 0 at include/net/sock.h:1974 ip_finish_output2+0x34f/0x360()
[  222.308027] Modules linked in: cfg80211 joydev crct10dif_pclmul crc32_pclmul aesni_intel aes_x86_64 glue_helper hid_generic lrw gf128mul ablk_helper i2c_piix4 hid_hyperv hyperv_fb hid cryptd hyperv_keyboard 8250_fintek mac_hid serio_raw parport_pc ppdev lp parport autofs4 hv_utils hv_netvsc hv_storvsc psmouse hv_vmbus floppy pata_acpi
[  222.308088] CPU: 6 PID: 0 Comm: swapper/6 Not tainted 4.3.0-rc6-next-20151022+ #2
[  222.308104] Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS 090006  05/23/2012
[  222.308120]  ffffffff81b2ae66 ffff88007c783878 ffffffff813a4cf4 0000000000000000
[  222.308137]  ffff88007c7838b0 ffffffff81078cc6 ffff88005bf2dc00 ffff880079f58000
[  222.308153]  ffff88005bf2c000 ffff88005bf2c800 ffff880050b28000 ffff88007c7838c0
[  222.308171] Call Trace:
[  222.308185]  <IRQ>  [<ffffffff813a4cf4>] dump_stack+0x44/0x60
[  222.308212]  [<ffffffff81078cc6>] warn_slowpath_common+0x86/0xc0
[  222.308228]  [<ffffffff81078dba>] warn_slowpath_null+0x1a/0x20
[  222.308245]  [<ffffffff816d2e6f>] ip_finish_output2+0x34f/0x360
[  222.308262]  [<ffffffff816d4589>] ip_finish_output+0x149/0x1e0
[  222.308280]  [<ffffffff816d4f2c>] ip_output+0x5c/0xc0
[  222.308300]  [<ffffffff8101e899>] ? sched_clock+0x9/0x10
[  222.308319]  [<ffffffff810a63a7>] ? sched_clock_local+0x17/0x80
[  222.308335]  [<ffffffff816d4725>] ip_local_out+0x35/0x40
[  222.308351]  [<ffffffff816d487d>] ip_build_and_send_pkt+0x14d/0x1c0
[  222.308369]  [<ffffffff816f39fb>] tcp_v4_send_synack+0x5b/0xb0
[  222.308386]  [<ffffffff816d8fb9>] ? inet_ehash_insert+0x59/0x130
[  222.308404]  [<ffffffff816da266>] ? inet_csk_reqsk_queue_hash_add+0x76/0xa0
[  222.308425]  [<ffffffff816e3223>] tcp_conn_request+0x9b3/0x9f0
[  222.308444]  [<ffffffff816f20bc>] tcp_v4_conn_request+0x4c/0x50
[  222.308458]  [<ffffffff816e940c>] tcp_rcv_state_process+0x19c/0xcb0
[  222.308473]  [<ffffffff817746ec>] ? tcp_v4_inbound_md5_hash+0x6d/0x177
[  222.308485]  [<ffffffff816f2f53>] tcp_v4_do_rcv+0x73/0x210
[  222.308496]  [<ffffffff816f43b1>] tcp_v4_rcv+0x811/0x840
[  222.308511]  [<ffffffff816cda9a>] ? ip_route_input_noref+0xb3a/0xd90
[  222.308524]  [<ffffffff816cf1a3>] ip_local_deliver_finish+0x53/0xe0
[  222.308536]  [<ffffffff816cf690>] ip_local_deliver+0x60/0xd0
[  222.308549]  [<ffffffff816cf2b7>] ip_rcv_finish+0x87/0x2b0
[  222.308561]  [<ffffffff816cf949>] ip_rcv+0x249/0x350
[  222.308574]  [<ffffffff8176796c>] ? packet_rcv+0x4c/0x3e0
[  222.308589]  [<ffffffff81696857>] __netif_receive_skb_core+0x2d7/0x980
[  222.308602]  [<ffffffff81696f18>] __netif_receive_skb+0x18/0x60
[  222.308614]  [<ffffffff81697b38>] process_backlog+0xa8/0x150
[  222.308627]  [<ffffffff816973c3>] net_rx_action+0x1b3/0x2c0
[  222.308641]  [<ffffffff8107d32c>] __do_softirq+0xfc/0x250
[  222.308653]  [<ffffffff8107d5de>] irq_exit+0x8e/0x90
[  222.308667]  [<ffffffff8104a1ce>] hyperv_vector_handler+0x3e/0x50
[  222.308680]  [<ffffffff817835c2>] hyperv_callback_vector+0x82/0x90
[  222.308690]  <EOI>  [<ffffffff8105e256>] ? native_safe_halt+0x6/0x10
[  222.308707]  [<ffffffff8101f7ae>] default_idle+0x1e/0xa0
[  222.308718]  [<ffffffff8101feff>] arch_cpu_idle+0xf/0x20
[  222.308731]  [<ffffffff810b86f2>] default_idle_call+0x32/0x40
[  222.308743]  [<ffffffff810b8a18>] cpu_startup_entry+0x2b8/0x310
[  222.308756]  [<ffffffff8104c238>] start_secondary+0x178/0x1a0
[  222.308769] ---[ end trace 0c71438d4d1b6dca ]---

Thanks,
- Haiyang

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