Re: [PATCH net,v2] tcp: make sure init the accept_queue's spinlocks once

[Paolo Abeni <pabeni@redhat.com>]

On Sat, 2024-01-13 at 11:07 +0800, Zhengchao Shao wrote:
> When I run syz's reproduction C program locally, it causes the following
> issue:
> pvqspinlock: lock 0xffff9d181cd5c660 has corrupted value 0x0!
> WARNING: CPU: 19 PID: 21160 at __pv_queued_spin_unlock_slowpath (kernel/locking/qspinlock_paravirt.h:508)
> Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
> RIP: 0010:__pv_queued_spin_unlock_slowpath (kernel/locking/qspinlock_paravirt.h:508)
> Code: 73 56 3a ff 90 c3 cc cc cc cc 8b 05 bb 1f 48 01 85 c0 74 05 c3 cc cc cc cc 8b 17 48 89 fe 48 c7 c7
> 30 20 ce 8f e8 ad 56 42 ff <0f> 0b c3 cc cc cc cc 0f 0b 0f 1f 40 00 90 90 90 90 90 90 90 90 90
> RSP: 0018:ffffa8d200604cb8 EFLAGS: 00010282
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff9d1ef60e0908
> RDX: 00000000ffffffd8 RSI: 0000000000000027 RDI: ffff9d1ef60e0900
> RBP: ffff9d181cd5c280 R08: 0000000000000000 R09: 00000000ffff7fff
> R10: ffffa8d200604b68 R11: ffffffff907dcdc8 R12: 0000000000000000
> R13: ffff9d181cd5c660 R14: ffff9d1813a3f330 R15: 0000000000001000
> FS:  00007fa110184640(0000) GS:ffff9d1ef60c0000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000020000000 CR3: 000000011f65e000 CR4: 00000000000006f0
> Call Trace:
> <IRQ>
>   _raw_spin_unlock (kernel/locking/spinlock.c:186)
>   inet_csk_reqsk_queue_add (net/ipv4/inet_connection_sock.c:1321)
>   inet_csk_complete_hashdance (net/ipv4/inet_connection_sock.c:1358)
>   tcp_check_req (net/ipv4/tcp_minisocks.c:868)
>   tcp_v4_rcv (net/ipv4/tcp_ipv4.c:2260)
>   ip_protocol_deliver_rcu (net/ipv4/ip_input.c:205)
>   ip_local_deliver_finish (net/ipv4/ip_input.c:234)
>   __netif_receive_skb_one_core (net/core/dev.c:5529)
>   process_backlog (./include/linux/rcupdate.h:779)
>   __napi_poll (net/core/dev.c:6533)
>   net_rx_action (net/core/dev.c:6604)
>   __do_softirq (./arch/x86/include/asm/jump_label.h:27)
>   do_softirq (kernel/softirq.c:454 kernel/softirq.c:441)
> </IRQ>
> <TASK>
>   __local_bh_enable_ip (kernel/softirq.c:381)
>   __dev_queue_xmit (net/core/dev.c:4374)
>   ip_finish_output2 (./include/net/neighbour.h:540 net/ipv4/ip_output.c:235)
>   __ip_queue_xmit (net/ipv4/ip_output.c:535)
>   __tcp_transmit_skb (net/ipv4/tcp_output.c:1462)
>   tcp_rcv_synsent_state_process (net/ipv4/tcp_input.c:6469)
>   tcp_rcv_state_process (net/ipv4/tcp_input.c:6657)
>   tcp_v4_do_rcv (net/ipv4/tcp_ipv4.c:1929)
>   __release_sock (./include/net/sock.h:1121 net/core/sock.c:2968)
>   release_sock (net/core/sock.c:3536)
>   inet_wait_for_connect (net/ipv4/af_inet.c:609)
>   __inet_stream_connect (net/ipv4/af_inet.c:702)
>   inet_stream_connect (net/ipv4/af_inet.c:748)
>   __sys_connect (./include/linux/file.h:45 net/socket.c:2064)
>   __x64_sys_connect (net/socket.c:2073 net/socket.c:2070 net/socket.c:2070)
>   do_syscall_64 (arch/x86/entry/common.c:51 arch/x86/entry/common.c:82)
>   entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:129)
>   RIP: 0033:0x7fa10ff05a3d
>   Code: 5b 41 5c c3 66 0f 1f 84 00 00 00 00 00 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89
>   c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d ab a3 0e 00 f7 d8 64 89 01 48
>   RSP: 002b:00007fa110183de8 EFLAGS: 00000202 ORIG_RAX: 000000000000002a
>   RAX: ffffffffffffffda RBX: 0000000020000054 RCX: 00007fa10ff05a3d
>   RDX: 000000000000001c RSI: 0000000020000040 RDI: 0000000000000003
>   RBP: 00007fa110183e20 R08: 0000000000000000 R09: 0000000000000000
>   R10: 0000000000000000 R11: 0000000000000202 R12: 00007fa110184640
>   R13: 0000000000000000 R14: 00007fa10fe8b060 R15: 00007fff73e23b20
> </TASK>
> 
> The issue triggering process is analyzed as follows:
> Thread A                                       Thread B
> tcp_v4_rcv	//receive ack TCP packet       inet_shutdown
>   tcp_check_req                                  tcp_disconnect //disconnect sock
>   ...                                              tcp_set_state(sk, TCP_CLOSE)
>     inet_csk_complete_hashdance                ...
>       inet_csk_reqsk_queue_add                 inet_listen  //start listen
>         spin_lock(&queue->rskq_lock)             inet_csk_listen_start
>         ...                                        reqsk_queue_alloc
>         ...                                          spin_lock_init
>         spin_unlock(&queue->rskq_lock)	//warning
> 
> When the socket receives the ACK packet during the three-way handshake,
> it will hold spinlock. And then the user actively shutdowns the socket
> and listens to the socket immediately, the spinlock will be initialized.
> When the socket is going to release the spinlock, a warning is generated.
> Also the same issue to fastopenq.lock.
> 
> Add 'init_done' to make sure init the accept_queue's spinlocks once.
> 
> Fixes: fff1f3001cc5 ("tcp: add a spinlock to protect struct request_sock_queue")
> Fixes: 168a8f58059a ("tcp: TCP Fast Open Server - main code path")
> Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
> ---
> v2: Add 'init_done' to make sure init the accept_queue's spinlocks once.
> ---
>  include/net/request_sock.h | 1 +
>  net/core/request_sock.c    | 7 +++++--
>  net/ipv4/tcp.c             | 1 +
>  3 files changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/include/net/request_sock.h b/include/net/request_sock.h
> index 144c39db9898..0054746fe92d 100644
> --- a/include/net/request_sock.h
> +++ b/include/net/request_sock.h
> @@ -175,6 +175,7 @@ struct fastopen_queue {
>  struct request_sock_queue {
>  	spinlock_t		rskq_lock;
>  	u8			rskq_defer_accept;
> +	bool			init_done;
>  
>  	u32			synflood_warned;
>  	atomic_t		qlen;
> diff --git a/net/core/request_sock.c b/net/core/request_sock.c
> index f35c2e998406..51fe631a4af2 100644
> --- a/net/core/request_sock.c
> +++ b/net/core/request_sock.c
> @@ -33,9 +33,12 @@
>  
>  void reqsk_queue_alloc(struct request_sock_queue *queue)
>  {
> -	spin_lock_init(&queue->rskq_lock);
> +	if (!queue->init_done) {
> +		spin_lock_init(&queue->rskq_lock);
> +		spin_lock_init(&queue->fastopenq.lock);
> +		queue->init_done = true;
> +	}
>  
> -	spin_lock_init(&queue->fastopenq.lock);
>  	queue->fastopenq.rskq_rst_head = NULL;
>  	queue->fastopenq.rskq_rst_tail = NULL;
>  	queue->fastopenq.qlen = 0;

I looks like the last bits of reqsk_queue_alloc() could still race with
a 3rd ack. Could the latter end-up touching a corrupted/unexpectedly
zeroed fastopenq?

Cheers,

Paolo