WARNING: bad unlock balance in mptcp_listen

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 5b8b9d0c Merge branch 'akpm' (patches from Andrew)
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1712bdb3e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=23c5a352e32a1944
dashboard link: https://syzkaller.appspot.com/bug?extid=ffec3741d41140477097
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

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

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+ffec37...@syzkaller.appspotmail.com

=====================================
WARNING: bad unlock balance detected!
5.6.0-syzkaller #0 Not tainted
-------------------------------------
syz-executor.0/25417 is trying to release lock (sk_lock-AF_INET6) at:
[<ffffffff87c65063>] mptcp_listen+0x1c3/0x2e0 net/mptcp/protocol.c:1783
but there are no more locks to release!

other info that might help us debug this:
1 lock held by syz-executor.0/25417:
#0: ffff888048fcf260 (slock-AF_INET6){+.-.}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:358 [inline]
#0: ffff888048fcf260 (slock-AF_INET6){+.-.}-{2:2}, at: release_sock+0x1b/0x1b0 net/core/sock.c:2974

stack backtrace:
CPU: 0 PID: 25417 Comm: syz-executor.0 Not tainted 5.6.0-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+0x188/0x20d lib/dump_stack.c:118
__lock_release kernel/locking/lockdep.c:4633 [inline]
lock_release+0x586/0x800 kernel/locking/lockdep.c:4941
sock_release_ownership include/net/sock.h:1539 [inline]
release_sock+0x177/0x1b0 net/core/sock.c:2984
mptcp_listen+0x1c3/0x2e0 net/mptcp/protocol.c:1783
__sys_listen+0x17d/0x250 net/socket.c:1696
__do_sys_listen net/socket.c:1705 [inline]
__se_sys_listen net/socket.c:1703 [inline]
__x64_sys_listen+0x50/0x70 net/socket.c:1703
do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
entry_SYSCALL_64_after_hwframe+0x49/0xb3
RIP: 0033:0x45c889
Code: ad b6 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 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fcb5e5dac78 EFLAGS: 00000246 ORIG_RAX: 0000000000000032
RAX: ffffffffffffffda RBX: 00007fcb5e5db6d4 RCX: 000000000045c889
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 000000000076bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000712 R14: 00000000004c9e2d R15: 000000000076bf0c


---
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[Florian Westphal]

syzbot <syzbot+ffec37...@syzkaller.appspotmail.com> wrote:
> syzbot found the following crash on:
>
> HEAD commit: 5b8b9d0c Merge branch 'akpm' (patches from Andrew)
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1712bdb3e00000
> kernel config: https://syzkaller.appspot.com/x/.config?x=23c5a352e32a1944
> dashboard link: https://syzkaller.appspot.com/bug?extid=ffec3741d41140477097
> compiler: gcc (GCC) 9.0.0 20181231 (experimental)
>
> Unfortunately, I don't have any reproducer for this crash yet.
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+ffec37...@syzkaller.appspotmail.com
>
> =====================================
> WARNING: bad unlock balance detected!
> 5.6.0-syzkaller #0 Not tainted
> -------------------------------------
> syz-executor.0/25417 is trying to release lock (sk_lock-AF_INET6) at:
> [<ffffffff87c65063>] mptcp_listen+0x1c3/0x2e0 net/mptcp/protocol.c:1783
> but there are no more locks to release!

#syz dup: WARNING: bad unlock balance in mptcp_poll