=====================================
[ BUG: bad unlock balance detected! ]
4.9.77-ge12a9c4 #18 Not tainted
-------------------------------------
syz-executor3/27328 is trying to release lock (mrt_lock) at:
[<ffffffff834e8764>] 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 syz-executor3/27328:
 #0:  (&p->lock){+.+.+.}, at: [<ffffffff815e85fd>] seq_read+0xdd/0x1290 fs/seq_file.c:178

stack backtrace:
CPU: 1 PID: 27328 Comm: syz-executor3 Not tainted 4.9.77-ge12a9c4 #18
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801c28a7948 ffffffff81d941c9 ffffffff849b6b78 ffff8801c8eac800
 ffffffff834e8764 ffffffff849b6b78 ffff8801c8ead088 ffff8801c28a7978
 ffffffff81237d24 dffffc0000000000 ffffffff849b6b78 00000000ffffffff
Call Trace:
 [<ffffffff81d941c9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d941c9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81237d24>] print_unlock_imbalance_bug+0x174/0x1a0 kernel/locking/lockdep.c:3398
 [<ffffffff812407f8>] __lock_release kernel/locking/lockdep.c:3540 [inline]
 [<ffffffff812407f8>] lock_release+0x6f8/0xb80 kernel/locking/lockdep.c:3775
 [<ffffffff838b279a>] __raw_read_unlock include/linux/rwlock_api_smp.h:225 [inline]
 [<ffffffff838b279a>] _raw_read_unlock+0x1a/0x50 kernel/locking/spinlock.c:255
 [<ffffffff834e8764>] ipmr_mfc_seq_stop+0xe4/0x140 net/ipv6/ip6mr.c:553
 [<ffffffff815e8fa3>] seq_read+0xa83/0x1290 fs/seq_file.c:283
 [<ffffffff816c1c9f>] proc_reg_read+0xef/0x170 fs/proc/inode.c:202
 [<ffffffff8156c5c1>] do_loop_readv_writev.part.17+0x141/0x1e0 fs/read_write.c:714
 [<ffffffff81570430>] do_loop_readv_writev fs/read_write.c:880 [inline]
 [<ffffffff81570430>] do_readv_writev+0x520/0x750 fs/read_write.c:874
 [<ffffffff815706e4>] vfs_readv+0x84/0xc0 fs/read_write.c:898
 [<ffffffff81570a85>] do_preadv+0x115/0x1a0 fs/read_write.c:975
 [<ffffffff81573d60>] SYSC_preadv fs/read_write.c:1025 [inline]
 [<ffffffff81573d60>] SyS_preadv+0x30/0x40 fs/read_write.c:1020
 [<ffffffff838b2c2e>] entry_SYSCALL_64_fastpath+0x29/0xe8