=====================================
[ BUG: bad unlock balance detected! ]
4.9.79-g71f1469 #25 Not tainted
-------------------------------------
syz-executor4/9448 is trying to release lock (mrt_lock) at:
[<ffffffff834e8ee4>] ipmr_mfc_seq_stop+0xe4/0x140 net/ipv6/ip6mr.c:553
audit: type=1400 audit(1517443776.710:43): avc:  denied  { sys_chroot } for  pid=9460 comm="syz-executor2" capability=18  scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=cap_userns permissive=1
but there are no more locks to release!

other info that might help us debug this:
2 locks held by syz-executor4/9448:
 #0:  (sb_writers#7){.+.+.+}, at: [<ffffffff81572e4f>] file_start_write include/linux/fs.h:2621 [inline]
 #0:  (sb_writers#7){.+.+.+}, at: [<ffffffff81572e4f>] do_sendfile+0x9ff/0xd30 fs/read_write.c:1400
 #1:  (&p->lock){+.+.+.}, at: [<ffffffff815e8b6d>] seq_read+0xdd/0x1290 fs/seq_file.c:178

stack backtrace:
CPU: 1 PID: 9448 Comm: syz-executor4 Not tainted 4.9.79-g71f1469 #25
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801c43b72a8 ffffffff81d94829 ffffffff849b6cb8 ffff8801c9ccc800
 ffffffff834e8ee4 ffffffff849b6cb8 ffff8801c9ccd088 ffff8801c43b72d8
 ffffffff81237df4 dffffc0000000000 ffffffff849b6cb8 00000000ffffffff
Call Trace:
 [<ffffffff81d94829>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d94829>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81237df4>] print_unlock_imbalance_bug+0x174/0x1a0 kernel/locking/lockdep.c:3398
 [<ffffffff812408c8>] __lock_release kernel/locking/lockdep.c:3540 [inline]
 [<ffffffff812408c8>] lock_release+0x6f8/0xb80 kernel/locking/lockdep.c:3775
 [<ffffffff838b2fda>] __raw_read_unlock include/linux/rwlock_api_smp.h:225 [inline]
 [<ffffffff838b2fda>] _raw_read_unlock+0x1a/0x50 kernel/locking/spinlock.c:255
 [<ffffffff834e8ee4>] ipmr_mfc_seq_stop+0xe4/0x140 net/ipv6/ip6mr.c:553
 [<ffffffff815e9513>] seq_read+0xa83/0x1290 fs/seq_file.c:283
 [<ffffffff816c220f>] proc_reg_read+0xef/0x170 fs/proc/inode.c:202
 [<ffffffff8156cab1>] do_loop_readv_writev.part.17+0x141/0x1e0 fs/read_write.c:714
 [<ffffffff81570920>] do_loop_readv_writev fs/read_write.c:880 [inline]
 [<ffffffff81570920>] do_readv_writev+0x520/0x750 fs/read_write.c:874
 [<ffffffff81570bd4>] vfs_readv+0x84/0xc0 fs/read_write.c:898
 [<ffffffff8160fd0f>] kernel_readv fs/splice.c:363 [inline]
 [<ffffffff8160fd0f>] default_file_splice_read+0x43f/0x7a0 fs/splice.c:435
 [<ffffffff8160ee0a>] do_splice_to+0x10a/0x160 fs/splice.c:899
 [<ffffffff8160f0ad>] splice_direct_to_actor+0x24d/0x800 fs/splice.c:971
 [<ffffffff8160f807>] do_splice_direct+0x1a7/0x270 fs/splice.c:1080
 [<ffffffff8157299b>] do_sendfile+0x54b/0xd30 fs/read_write.c:1401
 [<ffffffff815748f1>] SYSC_sendfile64 fs/read_write.c:1456 [inline]
 [<ffffffff815748f1>] SyS_sendfile64+0xd1/0x160 fs/read_write.c:1448
 [<ffffffff838b346e>] entry_SYSCALL_64_fastpath+0x29/0xe8
mip6: mip6_destopt_init_state: spi is not 0: 3540254720
mip6: mip6_destopt_init_state: spi is not 0: 3540254720
keychord: unsupported version 0