=====================================
WARNING: bad unlock balance detected!
5.6.0-syzkaller #0 Not tainted
-------------------------------------
syz-executor473/7733 is trying to release lock (sk_lock-AF_INET6) at:
[<ffffffff87c51839>] mptcp_poll+0xb9/0x530 net/mptcp/protocol.c:1856
but there are no more locks to release!
other info that might help us debug this:
1 lock held by syz-executor473/7733:
#0: ffff88808fe2f0a0 (slock-AF_INET6){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:358 [inline]
#0: ffff88808fe2f0a0 (slock-AF_INET6){+...}-{2:2}, at: release_sock+0x1b/0x1b0 net/core/sock.c:2974
stack backtrace:
CPU: 0 PID: 7733 Comm: syz-executor473 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_poll+0xb9/0x530 net/mptcp/protocol.c:1856
sock_poll+0x15c/0x470 net/socket.c:1271
vfs_poll include/linux/poll.h:90 [inline]
do_pollfd fs/select.c:859 [inline]
do_poll fs/select.c:907 [inline]
do_sys_poll+0x63c/0xdd0 fs/select.c:1001
__do_sys_ppoll fs/select.c:1101 [inline]
__se_sys_ppoll fs/select.c:1081 [inline]
__x64_sys_ppoll+0x210/0x280 fs/select.c:1081
do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
entry_SYSCALL_64_after_hwframe+0x49/0xb3
RIP: 0033:0x441219
Code: e8 fc ab 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 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 0f 83 9b 09 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fff9deb18e8 EFLAGS: 00000246 ORIG_RAX: 000000000000010f
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000441219
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000020000080
RBP: 000000000000f233 R08: 3f00000000000000 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000402040
R13: 00000000004020d0 R14: 0000000000000000 R15: 0000000000000000