------------[ cut here ]------------
WARNING: CPU: 0 PID: 23287 at net/ipv4/tcp_input.c:2573 tcp_cwnd_reduction+0x329/0x390 net/ipv4/tcp_input.c:2573
Modules linked in:
CPU: 0 PID: 23287 Comm: syz-executor.3 Not tainted 5.11.0-rc4-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 9a 38 fb f9 e8 95 38 fb f9 44 39 e5 41 0f 4f ec eb 81 e8 87 38 fb f9 <0f> 0b eb d6 e8 ce f8 3d fa e9 33 fd ff ff e8 c4 f8 3d fa e9 1c fe
RSP: 0018:ffffc9000944f6d8 EFLAGS: 00010212
RAX: 000000000000aab7 RBX: ffff88801d302f00 RCX: ffffc9000f8dc000
RDX: 0000000000040000 RSI: ffffffff877791f9 RDI: 0000000000000003
RBP: ffffc9000944f8d8 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff87778f4b R11: 0000000000000000 R12: 0000000000000003
R13: 0000000000000000 R14: 0000000000000004 R15: ffff88801d302f00
FS:  00007fb71b4b7700(0000) GS:ffff8880b9e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000004e75f0 CR3: 00000000184f4000 CR4: 0000000000350ef0
Call Trace:
 tcp_cong_control net/ipv4/tcp_input.c:3438 [inline]
 tcp_ack+0x418a/0x59f0 net/ipv4/tcp_input.c:3841
 tcp_rcv_established+0x130e/0x1eb0 net/ipv4/tcp_input.c:5801
 tcp_v4_do_rcv+0x5d1/0x870 net/ipv4/tcp_ipv4.c:1676
 sk_backlog_rcv include/net/sock.h:1016 [inline]
 __release_sock+0x134/0x3a0 net/core/sock.c:2542
 __sk_flush_backlog+0x22/0x30 net/core/sock.c:2562
 sk_flush_backlog include/net/sock.h:1103 [inline]
 tcp_sendmsg_locked+0x2763/0x2d90 net/ipv4/tcp.c:1306
 tcp_sendmsg+0x2b/0x40 net/ipv4/tcp.c:1459
 inet_sendmsg+0x99/0xe0 net/ipv4/af_inet.c:817
 sock_sendmsg_nosec net/socket.c:652 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:672
 __sys_sendto+0x21c/0x320 net/socket.c:1975
 __do_sys_sendto net/socket.c:1987 [inline]
 __se_sys_sendto net/socket.c:1983 [inline]
 __x64_sys_sendto+0xdd/0x1b0 net/socket.c:1983
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45e219
Code: 0d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 db b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fb71b4b6c68 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 0000000000000006 RCX: 000000000045e219
RDX: 00000000fffffd46 RSI: 0000000020000240 RDI: 0000000000000003
RBP: 000000000119bfd8 R08: 0000000000000000 R09: 00000000000001f4
R10: 00000000000081f4 R11: 0000000000000246 R12: 000000000119bf8c
R13: 00007ffde57de5af R14: 00007fb71b4b79c0 R15: 000000000119bf8c