[syzbot] [net?] WARNING in sk_nulls_del_node_init_rcu

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c055fc00c07b net/rds: fix WARNING in rds_conn_connect_if_d..
git tree: net
console output: https://syzkaller.appspot.com/x/log.txt?x=16aa17f2180000
kernel config: https://syzkaller.appspot.com/x/.config?x=fad652894fc96962
dashboard link: https://syzkaller.appspot.com/bug?extid=12c506c1aae251e70449
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c39eb6fb3ad1/disk-c055fc00.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/110f1226eb89/vmlinux-c055fc00.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1303e2df5cc4/bzImage-c055fc00.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+12c506...@syzkaller.appspotmail.com

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 000000000000000b R14: 00007f3b817abf80 R15: 00007ffd3beb57b8
</TASK>
------------[ cut here ]------------
WARNING: CPU: 0 PID: 23948 at include/net/sock.h:799 sk_nulls_del_node_init_rcu+0x166/0x1a0 include/net/sock.h:799
Modules linked in:
CPU: 0 PID: 23948 Comm: syz-executor.2 Not tainted 6.8.0-rc6-syzkaller-00159-gc055fc00c07b #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
RIP: 0010:sk_nulls_del_node_init_rcu+0x166/0x1a0 include/net/sock.h:799
Code: e8 7f 71 c6 f7 83 fb 02 7c 25 e8 35 6d c6 f7 4d 85 f6 0f 95 c0 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc e8 1b 6d c6 f7 90 <0f> 0b 90 eb b2 e8 10 6d c6 f7 4c 89 e7 be 04 00 00 00 e8 63 e7 d2
RSP: 0018:ffffc900032d7848 EFLAGS: 00010246
RAX: ffffffff89cd0035 RBX: 0000000000000001 RCX: 0000000000040000
RDX: ffffc90004de1000 RSI: 000000000003ffff RDI: 0000000000040000
RBP: 1ffff1100439ac26 R08: ffffffff89ccffe3 R09: 1ffff1100439ac28
R10: dffffc0000000000 R11: ffffed100439ac29 R12: ffff888021cd6140
R13: dffffc0000000000 R14: ffff88802a9bf5c0 R15: ffff888021cd6130
FS: 00007f3b823f16c0(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f3b823f0ff8 CR3: 000000004674a000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
__inet_hash_connect+0x140f/0x20b0 net/ipv4/inet_hashtables.c:1139
dccp_v6_connect+0xcb9/0x1480 net/dccp/ipv6.c:956
__inet_stream_connect+0x262/0xf30 net/ipv4/af_inet.c:678
inet_stream_connect+0x65/0xa0 net/ipv4/af_inet.c:749
__sys_connect_file net/socket.c:2048 [inline]
__sys_connect+0x2df/0x310 net/socket.c:2065
__do_sys_connect net/socket.c:2075 [inline]
__se_sys_connect net/socket.c:2072 [inline]
__x64_sys_connect+0x7a/0x90 net/socket.c:2072
do_syscall_64+0xf9/0x240
entry_SYSCALL_64_after_hwframe+0x6f/0x77
RIP: 0033:0x7f3b8167dda9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 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 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f3b823f10c8 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 00007f3b817abf80 RCX: 00007f3b8167dda9
RDX: 000000000000001c RSI: 0000000020000040 RDI: 0000000000000003
RBP: 00007f3b823f1120 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 000000000000000b R14: 00007f3b817abf80 R15: 00007ffd3beb57b8
</TASK>


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[Eric Dumazet]

CC Kuniyuki, because this is probably caused by

commit 66b60b0c8c4a163b022a9f0ad6769b0fd3dc662f
Author: Kuniyuki Iwashima <kun...@amazon.com>
Date: Wed Feb 14 11:13:08 2024 -0800

dccp/tcp: Unhash sk from ehash for tb2 alloc failure after
check_estalblished().

[Kuniyuki Iwashima]

From: Eric Dumazet <edum...@google.com>
Date: Fri, 8 Mar 2024 18:36:45 +0100

I'll look into it.

Thanks!

[Kuniyuki Iwashima]

From: syzbot <syzbot+12c506...@syzkaller.appspotmail.com>
Date: Fri, 08 Mar 2024 09:34:28 -0800

Here I had to use non-refcnt variant as check_established() doesn't
increment it.

I'll post a fix soon.

---8<---
diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index 308ff34002ea..4e470f18487f 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -1136,7 +1136,7 @@ int __inet_hash_connect(struct inet_timewait_death_row *death_row,
sock_prot_inuse_add(net, sk->sk_prot, -1);

spin_lock(lock);
- sk_nulls_del_node_init_rcu(sk);
+ __sk_nulls_del_node_init_rcu(sk);
spin_unlock(lock);

sk->sk_hash = 0;
---8<---