=====================================
WARNING: bad unlock balance detected!
4.15.0-rc7+ #260 Not tainted
-------------------------------------
syz-executor4/5920 is trying to release lock (mrt_lock) at:
[<000000008f412f26>] 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:
1 lock held by syz-executor4/5920:
 #0:  (&p->lock){+.+.}, at: [<00000000b6324230>] seq_read+0xd5/0x13d0 fs/seq_file.c:165

stack backtrace:
CPU: 0 PID: 5920 Comm: syz-executor4 Not tainted 4.15.0-rc7+ #260
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:3479
 __lock_release kernel/locking/lockdep.c:3685 [inline]
 lock_release+0x6fe/0xa40 kernel/locking/lockdep.c:3933
 __raw_read_unlock include/linux/rwlock_api_smp.h:225 [inline]
 _raw_read_unlock+0x1a/0x30 kernel/locking/spinlock.c:248
 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+0x3d2/0x5a0 fs/read_write.c:897
 vfs_readv+0x121/0x1c0 fs/read_write.c:959
 do_preadv+0x115/0x1a0 fs/read_write.c:1043
 SYSC_preadv fs/read_write.c:1093 [inline]
 SyS_preadv+0x30/0x40 fs/read_write.c:1088
 entry_SYSCALL_64_fastpath+0x23/0x9a
RIP: 0033:0x452cf9
RSP: 002b:00007f61394c5c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000127
RAX: ffffffffffffffda RBX: 00007f61394c6700 RCX: 0000000000452cf9
RDX: 000000000000000a RSI: 0000000020a4df60 RDI: 0000000000000013
RBP: 0000000000a2f870 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000212 R12: 0000000000000000
R13: 0000000000a2f7ef R14: 00007f61394c69c0 R15: 0000000000000002
BUG: sleeping function called from invalid context at lib/usercopy.c:25
in_atomic(): 1, irqs_disabled(): 0, pid: 5920, name: syz-executor4
INFO: lockdep is turned off.
CPU: 0 PID: 5920 Comm: syz-executor4 Not tainted 4.15.0-rc7+ #260
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
 ___might_sleep+0x2b2/0x470 kernel/sched/core.c:6060
 __might_sleep+0x95/0x190 kernel/sched/core.c:6013
 __might_fault+0xab/0x1d0 mm/memory.c:4526
 _copy_to_user+0x2c/0xc0 lib/usercopy.c:25
 copy_to_user include/linux/uaccess.h:155 [inline]
 seq_read+0x875/0x13d0 fs/seq_file.c:212
 proc_reg_read+0xef/0x170 fs/proc/inode.c:217
 do_loop_readv_writev fs/read_write.c:673 [inline]
 do_iter_read+0x3d2/0x5a0 fs/read_write.c:897
 vfs_readv+0x121/0x1c0 fs/read_write.c:959
 do_preadv+0x115/0x1a0 fs/read_write.c:1043
 SYSC_preadv fs/read_write.c:1093 [inline]
 SyS_preadv+0x30/0x40 fs/read_write.c:1088
 entry_SYSCALL_64_fastpath+0x23/0x9a
RIP: 0033:0x452cf9
RSP: 002b:00007f61394c5c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000127
RAX: ffffffffffffffda RBX: 00007f61394c6700 RCX: 0000000000452cf9
RDX: 000000000000000a RSI: 0000000020a4df60 RDI: 0000000000000013
RBP: 0000000000a2f870 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000212 R12: 0000000000000000
R13: 0000000000a2f7ef R14: 00007f61394c69c0 R15: 0000000000000002
WARNING: CPU: 0 PID: 5920 at lib/usercopy.c:26 _copy_to_user+0xb5/0xc0 lib/usercopy.c:26