------------[ cut here ]------------
WARNING: CPU: 0 PID: 12 at net/ipv4/tcp_input.c:2573 tcp_cwnd_reduction+0x329/0x390 net/ipv4/tcp_input.c:2573
Modules linked in:
CPU: 0 PID: 12 Comm: ksoftirqd/0 Not tainted 5.11.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:tcp_cwnd_reduction+0x329/0x390 net/ipv4/tcp_input.c:2573
Code: 40 09 00 00 48 83 c4 18 5b 5d 41 5c 41 5d 41 5e 41 5f e9 aa 9a fa f9 e8 a5 9a fa f9 44 39 e5 41 0f 4f ec eb 81 e8 97 9a fa f9 <0f> 0b eb d6 e8 ae 75 3d fa e9 33 fd ff ff e8 a4 75 3d fa e9 1c fe
RSP: 0018:ffffc90000d175b8 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff88806f352f00 RCX: 0000000000000100
RDX: ffff88801195d340 RSI: ffffffff87783a09 RDI: 0000000000000003
RBP: ffffc90000d177b8 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff8778375b R11: 0000000000000000 R12: 0000000000000002
R13: 0000000000000000 R14: 0000000000000004 R15: ffff88806f352f00
FS:  0000000000000000(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2cd25000 CR3: 0000000068664000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 tcp_cong_control net/ipv4/tcp_input.c:3439 [inline]
 tcp_ack+0x40e3/0x59d0 net/ipv4/tcp_input.c:3843
 tcp_rcv_established+0x56b/0x1eb0 net/ipv4/tcp_input.c:5879
 tcp_v4_do_rcv+0x5d1/0x870 net/ipv4/tcp_ipv4.c:1676
 tcp_v4_rcv+0x2d36/0x3780 net/ipv4/tcp_ipv4.c:2059
 ip_protocol_deliver_rcu+0x5c/0x8a0 net/ipv4/ip_input.c:204
 ip_local_deliver_finish+0x20a/0x370 net/ipv4/ip_input.c:231
 NF_HOOK include/linux/netfilter.h:301 [inline]
 NF_HOOK include/linux/netfilter.h:295 [inline]
 ip_local_deliver+0x1b3/0x200 net/ipv4/ip_input.c:252
 dst_input include/net/dst.h:447 [inline]
 ip_rcv_finish+0x1da/0x2f0 net/ipv4/ip_input.c:428
 NF_HOOK include/linux/netfilter.h:301 [inline]
 NF_HOOK include/linux/netfilter.h:295 [inline]
 ip_rcv+0xaa/0xd0 net/ipv4/ip_input.c:539
 __netif_receive_skb_one_core+0x114/0x180 net/core/dev.c:5323
 __netif_receive_skb+0x27/0x1c0 net/core/dev.c:5437
 process_backlog+0x232/0x6c0 net/core/dev.c:6327
 napi_poll net/core/dev.c:6805 [inline]
 net_rx_action+0x461/0xe10 net/core/dev.c:6888
 __do_softirq+0x29b/0x9f6 kernel/softirq.c:343
 run_ksoftirqd kernel/softirq.c:650 [inline]
 run_ksoftirqd+0x2d/0x50 kernel/softirq.c:642
 smpboot_thread_fn+0x655/0x9e0 kernel/smpboot.c:165
 kthread+0x3b1/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296