WARNING in tcp_cwnd_reduction

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3f8a27f9e27b Linux 4.19.211
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=11453e68b00000
kernel config: https://syzkaller.appspot.com/x/.config?x=9b9277b418617afe
dashboard link: https://syzkaller.appspot.com/bug?extid=54355741864f749b988c
compiler: gcc version 10.2.1 20210110 (Debian 10.2.1-6)

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+543557...@syzkaller.appspotmail.com

WARNING: CPU: 0 PID: 28544 at net/ipv4/tcp_input.c:2474 tcp_cwnd_reduction+0x30e/0x370 net/ipv4/tcp_input.c:2474
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 28544 Comm: syz-executor.1 Not tainted 4.19.211-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1fc/0x2ef lib/dump_stack.c:118
panic+0x26a/0x50e kernel/panic.c:186
__warn.cold+0x20/0x5a kernel/panic.c:541
report_bug+0x262/0x2b0 lib/bug.c:183
fixup_bug arch/x86/kernel/traps.c:178 [inline]
fixup_bug arch/x86/kernel/traps.c:173 [inline]
do_error_trap+0x1d7/0x310 arch/x86/kernel/traps.c:296
invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:1038
RIP: 0010:tcp_cwnd_reduction+0x30e/0x370 net/ipv4/tcp_input.c:2474
Code: 29 eb e9 6f ff ff ff e8 90 38 88 fa 8b 44 24 14 44 29 e8 39 e8 0f 4d e8 83 c5 01 39 dd 0f 4e dd e9 51 ff ff ff e8 72 38 88 fa <0f> 0b eb a1 e8 c9 14 be fa e9 47 fd ff ff e8 bf 14 be fa e9 ea fe
RSP: 0018:ffff88808f64f6a8 EFLAGS: 00010212
RAX: 0000000000040000 RBX: ffffffff8b287140 RCX: ffffc90005f81000
RDX: 0000000000020cc5 RSI: ffffffff86da4cfe RDI: 0000000000000005
RBP: 0000000000000002 R08: ffff88808f64f8a8 R09: 0000000000000000
R10: 0000000000000005 R11: ffffffff8c66501b R12: 0000000000000000
R13: 0000000000005706 R14: ffff8880b4206e40 R15: ffff8880b4206e40
tcp_cong_control net/ipv4/tcp_input.c:3326 [inline]
tcp_ack+0x3e8a/0x51d0 net/ipv4/tcp_input.c:3719
tcp_rcv_established+0x66b/0x1ef0 net/ipv4/tcp_input.c:5670
tcp_v4_do_rcv+0x5d6/0x870 net/ipv4/tcp_ipv4.c:1547
sk_backlog_rcv include/net/sock.h:952 [inline]
__release_sock+0x134/0x3a0 net/core/sock.c:2362
__sk_flush_backlog+0x22/0x30 net/core/sock.c:2382
sk_flush_backlog include/net/sock.h:1039 [inline]
tcp_sendmsg_locked+0x2624/0x2f60 net/ipv4/tcp.c:1306
tcp_sendmsg+0x2b/0x40 net/ipv4/tcp.c:1462
inet_sendmsg+0x132/0x5a0 net/ipv4/af_inet.c:798
sock_sendmsg_nosec net/socket.c:651 [inline]
sock_sendmsg+0xc3/0x120 net/socket.c:661
__sys_sendto+0x21a/0x320 net/socket.c:1899
__do_sys_sendto net/socket.c:1911 [inline]
__se_sys_sendto net/socket.c:1907 [inline]
__x64_sys_sendto+0xdd/0x1b0 net/socket.c:1907
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7fdc3d15aa39
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fdc3a6af188 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007fdc3d25e020 RCX: 00007fdc3d15aa39
RDX: 00000000fffffd46 RSI: 0000000020000240 RDI: 0000000000000003
RBP: 00007fdc3d1b4c5f R08: 0000000000000000 R09: 00000000000001f4
R10: 00000000000081f4 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffec07a11af R14: 00007fdc3a6af300 R15: 0000000000022000
Kernel Offset: disabled
Rebooting in 86400 seconds..


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.