=====================================
[ BUG: bad unlock balance detected! ]
4.4.111-g1849cd3 #26 Not tainted
-------------------------------------
syz-executor0/17517 is trying to release lock (mrt_lock) at:
[<ffffffff833c9304>] 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:
2 locks held by syz-executor0/17517:
 #0:  (sb_writers#7){.+.+.+}, at: [<ffffffff81520644>] file_start_write include/linux/fs.h:2521 [inline]
 #0:  (sb_writers#7){.+.+.+}, at: [<ffffffff81520644>] do_sendfile+0x8e4/0xd30 fs/read_write.c:1226
 #1:  (&p->lock){+.+.+.}, at: [<ffffffff8158ce7d>] seq_read+0xdd/0x1270 fs/seq_file.c:178

stack backtrace:
CPU: 1 PID: 17517 Comm: syz-executor0 Not tainted 4.4.111-g1849cd3 #26
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 fa47f76aad3375c1 ffff8801d819f190 ffffffff81d0509d
 ffffffff84770798 ffff8801d9308000 ffffffff833c9304 ffffffff84770798
 ffff8801d9308848 ffff8801d819f1c0 ffffffff81232374 dffffc0000000000
Call Trace:
 [<ffffffff81d0509d>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d0509d>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff81232374>] print_unlock_imbalance_bug+0x174/0x1a0 kernel/locking/lockdep.c:3266
 [<ffffffff8123d21a>] __lock_release kernel/locking/lockdep.c:3408 [inline]
 [<ffffffff8123d21a>] lock_release+0x72a/0xc10 kernel/locking/lockdep.c:3611
 [<ffffffff8377519a>] __raw_read_unlock include/linux/rwlock_api_smp.h:225 [inline]
 [<ffffffff8377519a>] _raw_read_unlock+0x1a/0x50 kernel/locking/spinlock.c:255
 [<ffffffff833c9304>] ipmr_mfc_seq_stop+0xe4/0x140 net/ipv6/ip6mr.c:553
 [<ffffffff8158d820>] seq_read+0xa80/0x1270 fs/seq_file.c:283
 [<ffffffff81665cef>] proc_reg_read+0xef/0x170 fs/proc/inode.c:202
 [<ffffffff8151cc51>] do_loop_readv_writev+0x141/0x1e0 fs/read_write.c:680
 [<ffffffff8151efad>] do_readv_writev+0x5dd/0x6e0 fs/read_write.c:810
 [<ffffffff8151f128>] vfs_readv+0x78/0xb0 fs/read_write.c:834
 [<ffffffff815b9b9a>] kernel_readv fs/splice.c:586 [inline]
 [<ffffffff815b9b9a>] default_file_splice_read+0x4fa/0x8e0 fs/splice.c:662
 [<ffffffff815b58c5>] do_splice_to+0xf5/0x140 fs/splice.c:1154
 [<ffffffff815b5b60>] splice_direct_to_actor+0x250/0x830 fs/splice.c:1226
 [<ffffffff815b62e7>] do_splice_direct+0x1a7/0x270 fs/splice.c:1337
 [<ffffffff815202ac>] do_sendfile+0x54c/0xd30 fs/read_write.c:1227
 [<ffffffff81522323>] SYSC_sendfile64 fs/read_write.c:1282 [inline]
 [<ffffffff81522323>] SyS_sendfile64+0xc3/0x150 fs/read_write.c:1274
 [<ffffffff83775899>] entry_SYSCALL_64_fastpath+0x16/0x92
device gre0 entered promiscuous mode
audit: type=1400 audit(1515985067.079:53): avc:  denied  { ioctl } for  pid=21005 comm="syz-executor0" path="socket:[30060]" dev="sockfs" ino=30060 ioctlcmd=894c scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_generic_socket permissive=1