WARNING in smc_unhash_sk (2)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    e0a092eb Merge branch 'smc-next'
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=10fb322d200000
kernel config:  https://syzkaller.appspot.com/x/.config?x=94c460c3e4cd188a
dashboard link: https://syzkaller.appspot.com/bug?extid=bd8cc73d665590a1fcad
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=176c98f3200000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15ea286b200000

The bug was bisected to:

commit 50717a37db032ce783f50685a73bb2ac68471a5a
Author: Ursula Braun <ubraun@xxxxxxxxxxxxx>
Date:   Fri Apr 12 10:57:23 2019 +0000

    net/smc: nonblocking connect rework

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=14764e5b200000
final crash:    https://syzkaller.appspot.com/x/report.txt?x=16764e5b200000
console output: https://syzkaller.appspot.com/x/log.txt?x=12764e5b200000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+bd8cc73d665590a1fcad@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 50717a37db03 ("net/smc: nonblocking connect rework")

WARNING: CPU: 0 PID: 7716 at include/net/sock.h:666 sk_del_node_init  
include/net/sock.h:666 [inline]
WARNING: CPU: 0 PID: 7716 at include/net/sock.h:666  
smc_unhash_sk+0x1ea/0x260 net/smc/af_smc.c:95
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 7716 Comm: syz-executor514 Not tainted 5.1.0-rc4+ #135
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+0x172/0x1f0 lib/dump_stack.c:113
 panic+0x2cb/0x65c kernel/panic.c:214
 __warn.cold+0x20/0x45 kernel/panic.c:571
 report_bug+0x263/0x2b0 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:179 [inline]
 fixup_bug arch/x86/kernel/traps.c:174 [inline]
 do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:272
 do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:291
 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:973
RIP: 0010:sk_del_node_init include/net/sock.h:666 [inline]
RIP: 0010:smc_unhash_sk+0x1ea/0x260 net/smc/af_smc.c:95
Code: ff ff ff ff e8 57 e6 95 fe e8 82 9e 92 fa 4c 89 ef e8 ca 21 38 00 48  
83 c4 08 5b 41 5c 41 5d 41 5e 41 5f 5d c3 e8 66 9e 92 fa <0f> 0b eb 86 4c  
89 e7 e8 9a e7 ca fa e9 5f ff ff ff e8 b0 e7 ca fa
RSP: 0018:ffff888085e3fbd8 EFLAGS: 00010293
RAX: ffff888090874080 RBX: ffff8880914f9240 RCX: ffffffff86ddf01e
RDX: 0000000000000000 RSI: ffffffff86ddf09a RDI: 0000000000000005
RBP: ffff888085e3fc08 R08: ffff888090874080 R09: ffffed101229f259
R10: ffffed101229f258 R11: ffff8880914f92c3 R12: ffff8880914f92c0
R13: ffffffff895353e0 R14: ffff8880914f9268 R15: 0000000000000001
 smc_release+0x337/0x820 net/smc/af_smc.c:164
 __sock_release+0xd3/0x2b0 net/socket.c:599
 sock_close+0x1b/0x30 net/socket.c:1247
 __fput+0x2e5/0x8d0 fs/file_table.c:278
 ____fput+0x16/0x20 fs/file_table.c:309
 task_work_run+0x14a/0x1c0 kernel/task_work.c:113
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0x90a/0x2fa0 kernel/exit.c:876
 do_group_exit+0x135/0x370 kernel/exit.c:980
 __do_sys_exit_group kernel/exit.c:991 [inline]
 __se_sys_exit_group kernel/exit.c:989 [inline]
 __x64_sys_exit_group+0x44/0x50 kernel/exit.c:989
 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x43ee18
Code: Bad RIP value.
RSP: 002b:00007ffc9ebae588 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000043ee18
RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000
RBP: 00000000004be628 R08: 00000000000000e7 R09: ffffffffffffffd0
R10: 0000000000000004 R11: 0000000000000246 R12: 0000000000000001
R13: 00000000006d0180 R14: 0000000000000000 R15: 0000000000000000
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
This bug 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 syzkaller@xxxxxxxxxxxxxxxxx

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches