=====================================
WARNING: bad unlock balance detected!
4.15.0-rc2+ #118 Not tainted
-------------------------------------
syz-executor2/22120 is trying to release lock (mrt_lock) at:
[<00000000624d1c84>] ipmr_mfc_seq_stop+0xe1/0x130 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-executor2/22120:
 #0:  (sb_writers#6){.+.+}, at: [<000000007654fee9>] file_start_write include/linux/fs.h:2715 [inline]
 #0:  (sb_writers#6){.+.+}, at: [<000000007654fee9>] do_sendfile+0xaec/0xe90 fs/read_write.c:1412
 #1:  (&p->lock){+.+.}, at: [<00000000ba80d3e0>] seq_read+0xd5/0x13d0 fs/seq_file.c:165

stack backtrace:
CPU: 0 PID: 22120 Comm: syz-executor2 Not tainted 4.15.0-rc2+ #118
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:53
 print_unlock_imbalance_bug+0x12f/0x140 kernel/locking/lockdep.c:3561
 __lock_release kernel/locking/lockdep.c:3775 [inline]
 lock_release+0x5f9/0xda0 kernel/locking/lockdep.c:4023
 __raw_read_unlock include/linux/rwlock_api_smp.h:225 [inline]
 _raw_read_unlock+0x1a/0x30 kernel/locking/spinlock.c:255
 ipmr_mfc_seq_stop+0xe1/0x130 net/ipv6/ip6mr.c:553
 traverse+0x3bc/0xa00 fs/seq_file.c:135
 seq_read+0x96a/0x13d0 fs/seq_file.c:189
 proc_reg_read+0xef/0x170 fs/proc/inode.c:217
 do_loop_readv_writev fs/read_write.c:673 [inline]
 do_iter_read+0x3db/0x5b0 fs/read_write.c:897
 vfs_readv+0x121/0x1c0 fs/read_write.c:959
 kernel_readv fs/splice.c:361 [inline]
 default_file_splice_read+0x508/0xae0 fs/splice.c:416
 do_splice_to+0x110/0x170 fs/splice.c:880
 splice_direct_to_actor+0x242/0x820 fs/splice.c:952
 do_splice_direct+0x2a7/0x3d0 fs/splice.c:1061
 do_sendfile+0x5d5/0xe90 fs/read_write.c:1413
 C_SYSC_sendfile fs/read_write.c:1489 [inline]
 compat_SyS_sendfile+0xea/0x1a0 fs/read_write.c:1478
 do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline]
 do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389
 entry_SYSENTER_compat+0x51/0x60 arch/x86/entry/entry_64_compat.S:125
RIP: 0023:0xf7fc8c79
RSP: 002b:00000000f77c408c EFLAGS: 00000296 ORIG_RAX: 00000000000000bb
RAX: ffffffffffffffda RBX: 000000000000001b RCX: 000000000000001b
RDX: 0000000020f53ff8 RSI: 0000000000000091 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
WARNING: CPU: 0 PID: 22120 at lib/usercopy.c:26 _copy_to_user+0xb5/0xc0 lib/usercopy.c:26