syzbot

=====================================
[ BUG: bad unlock balance detected! ]
4.9.74-g9e5dd8e #12 Not tainted
-------------------------------------
syzkaller010086/3702 is trying to release lock (mrt_lock) at:
[<ffffffff834e5574>] ipmr_mfc_seq_stop+0xe4/0x140 net/ipv6/ip6mr.c:553
but there are no more locks to release!

other info that might help us debug this:
1 lock held by syzkaller010086/3702:
 #0:  (&p->lock){+.+.+.}, at: [<ffffffff815e5f6d>] seq_read+0xdd/0x1290 fs/seq_file.c:178

stack backtrace:
CPU: 1 PID: 3702 Comm: syzkaller010086 Not tainted 4.9.74-g9e5dd8e #12
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801c7eef878 ffffffff81d91d19 ffffffff849b0678 ffff8801c977c800
 ffffffff834e5574 ffffffff849b0678 ffff8801c977d088 ffff8801c7eef8a8
 ffffffff81235ad4 dffffc0000000000 ffffffff849b0678 00000000ffffffff
Call Trace:
 [<ffffffff81d91d19>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d91d19>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81235ad4>] print_unlock_imbalance_bug+0x174/0x1a0 kernel/locking/lockdep.c:3398
 [<ffffffff8123e5a8>] __lock_release kernel/locking/lockdep.c:3540 [inline]
 [<ffffffff8123e5a8>] lock_release+0x6f8/0xb80 kernel/locking/lockdep.c:3775
 [<ffffffff838af5fa>] __raw_read_unlock include/linux/rwlock_api_smp.h:225 [inline]
 [<ffffffff838af5fa>] _raw_read_unlock+0x1a/0x50 kernel/locking/spinlock.c:255
 [<ffffffff834e5574>] ipmr_mfc_seq_stop+0xe4/0x140 net/ipv6/ip6mr.c:553
 [<ffffffff815e2f27>] traverse+0x3a7/0x900 fs/seq_file.c:148
 [<ffffffff815e667a>] seq_read+0x7ea/0x1290 fs/seq_file.c:195
 [<ffffffff816bf60f>] proc_reg_read+0xef/0x170 fs/proc/inode.c:202
 [<ffffffff81569353>] __vfs_read+0x103/0x670 fs/read_write.c:452
 [<ffffffff8156d0ee>] vfs_read+0x11e/0x380 fs/read_write.c:475
 [<ffffffff815711df>] SYSC_pread64 fs/read_write.c:629 [inline]
 [<ffffffff815711df>] SyS_pread64+0x13f/0x170 fs/read_write.c:616
 [<ffffffff8111ab89>] sys32_pread+0x39/0x50 arch/x86/ia32/sys_ia32.c:179
 [<ffffffff81006fc7>] do_syscall_32_irqs_on arch/x86/entry/common.c:322 [inline]
 [<ffffffff81006fc7>] do_fast_syscall_32+0x2f7/0x890 arch/x86/entry/common.c:384
 [<ffffffff838b10e1>] entry_SYSENTER_compat+0x51/0x60 arch/x86/entry/entry_64_compat.S:124