=====================================
[ BUG: bad unlock balance detected! ]
4.9.80-g8a174b47 #31 Not tainted
-------------------------------------
syz-executor6/20761 is trying to release lock (mrt_lock) at:
[<ffffffff834e8f44>] ipmr_mfc_seq_stop+0xe4/0x140 net/ipv6/ip6mr.c:553
but there are no more locks to release!
FAULT_FLAG_ALLOW_RETRY missing 30
CPU: 1 PID: 20736 Comm: syz-executor4 Not tainted 4.9.80-g8a174b47 #31
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801cc3e75c0 ffffffff81d94be9 ffff8801cc3e78a0 0000000000000000
 ffff8801b6a2f910 ffff8801cc3e7790 ffff8801b6a2f800 ffff8801cc3e77b8
 ffffffff8166253a 0000000000000003 ffff8801cc3e7710 00000001d4090067
Call Trace:
 [<ffffffff81d94be9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d94be9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff8166253a>] handle_userfault+0xa3a/0x1310 fs/userfaultfd.c:323
 [<ffffffff814d0e21>] do_anonymous_page mm/memory.c:2747 [inline]
 [<ffffffff814d0e21>] handle_pte_fault mm/memory.c:3488 [inline]
 [<ffffffff814d0e21>] __handle_mm_fault mm/memory.c:3577 [inline]
 [<ffffffff814d0e21>] handle_mm_fault+0x1fd1/0x2530 mm/memory.c:3614
 [<ffffffff810de642>] __do_page_fault+0x5c2/0xd40 arch/x86/mm/fault.c:1407
 [<ffffffff810dede7>] do_page_fault+0x27/0x30 arch/x86/mm/fault.c:1470
 [<ffffffff838b4848>] page_fault+0x28/0x30 arch/x86/entry/entry_64.S:1055
 [<ffffffff82ed8f6f>] move_addr_to_kernel net/socket.c:190 [inline]
 [<ffffffff82ed8f6f>] copy_msghdr_from_user+0x3ef/0x550 net/socket.c:1876
 [<ffffffff82ed91c0>] ___sys_sendmsg+0xf0/0x7e0 net/socket.c:1916
 [<ffffffff82edb7d6>] __sys_sendmsg+0xd6/0x190 net/socket.c:2003
 [<ffffffff82edb8bd>] SYSC_sendmsg net/socket.c:2014 [inline]
 [<ffffffff82edb8bd>] SyS_sendmsg+0x2d/0x50 net/socket.c:2010
 [<ffffffff838b34ee>] entry_SYSCALL_64_fastpath+0x29/0xe8
FAULT_FLAG_ALLOW_RETRY missing 30
CPU: 1 PID: 20736 Comm: syz-executor4 Not tainted 4.9.80-g8a174b47 #31
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801cc3e75c0 ffffffff81d94be9 ffff8801cc3e78a0 0000000000000000
 ffff8801b6a2f790 ffff8801cc3e7790 ffff8801b6a2f680 ffff8801cc3e77b8
 ffffffff8166253a 1ffff1003987cebc ffff8801cc3e7710 00000001d4090067
Call Trace:
 [<ffffffff81d94be9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d94be9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff8166253a>] handle_userfault+0xa3a/0x1310 fs/userfaultfd.c:323
 [<ffffffff814d0e21>] do_anonymous_page mm/memory.c:2747 [inline]
 [<ffffffff814d0e21>] handle_pte_fault mm/memory.c:3488 [inline]
 [<ffffffff814d0e21>] __handle_mm_fault mm/memory.c:3577 [inline]
 [<ffffffff814d0e21>] handle_mm_fault+0x1fd1/0x2530 mm/memory.c:3614
 [<ffffffff810de642>] __do_page_fault+0x5c2/0xd40 arch/x86/mm/fault.c:1407
 [<ffffffff810dede7>] do_page_fault+0x27/0x30 arch/x86/mm/fault.c:1470
 [<ffffffff838b4848>] page_fault+0x28/0x30 arch/x86/entry/entry_64.S:1055
 [<ffffffff82ed8f6f>] move_addr_to_kernel net/socket.c:190 [inline]
 [<ffffffff82ed8f6f>] copy_msghdr_from_user+0x3ef/0x550 net/socket.c:1876
 [<ffffffff82ed91c0>] ___sys_sendmsg+0xf0/0x7e0 net/socket.c:1916
 [<ffffffff82edb7d6>] __sys_sendmsg+0xd6/0x190 net/socket.c:2003
 [<ffffffff82edb8bd>] SYSC_sendmsg net/socket.c:2014 [inline]
 [<ffffffff82edb8bd>] SyS_sendmsg+0x2d/0x50 net/socket.c:2010
 [<ffffffff838b34ee>] entry_SYSCALL_64_fastpath+0x29/0xe8

other info that might help us debug this:
2 locks held by syz-executor6/20761:
 #0:  (sb_writers#7){.+.+.+}, at: [<ffffffff8157303f>] file_start_write include/linux/fs.h:2621 [inline]
 #0:  (sb_writers#7){.+.+.+}, at: [<ffffffff8157303f>] do_sendfile+0x9ff/0xd30 fs/read_write.c:1400
 #1:  (&p->lock){+.+.+.}, at: [<ffffffff815e8edd>] seq_read+0xdd/0x1290 fs/seq_file.c:178

stack backtrace:
CPU: 0 PID: 20761 Comm: syz-executor6 Not tainted 4.9.80-g8a174b47 #31
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801b5d4f2a8 ffffffff81d94be9 ffffffff849b6cf8 ffff8801d5144800
 ffffffff834e8f44 ffffffff849b6cf8 ffff8801d5145088 ffff8801b5d4f2d8
 ffffffff81237e84 dffffc0000000000 ffffffff849b6cf8 00000000ffffffff
Call Trace:
 [<ffffffff81d94be9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d94be9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81237e84>] print_unlock_imbalance_bug+0x174/0x1a0 kernel/locking/lockdep.c:3398
 [<ffffffff81240958>] __lock_release kernel/locking/lockdep.c:3540 [inline]
 [<ffffffff81240958>] lock_release+0x6f8/0xb80 kernel/locking/lockdep.c:3775
 [<ffffffff838b303a>] __raw_read_unlock include/linux/rwlock_api_smp.h:225 [inline]
 [<ffffffff838b303a>] _raw_read_unlock+0x1a/0x50 kernel/locking/spinlock.c:255
 [<ffffffff834e8f44>] ipmr_mfc_seq_stop+0xe4/0x140 net/ipv6/ip6mr.c:553
 [<ffffffff815e9883>] seq_read+0xa83/0x1290 fs/seq_file.c:283
 [<ffffffff816c257f>] proc_reg_read+0xef/0x170 fs/proc/inode.c:202
 [<ffffffff8156cca1>] do_loop_readv_writev.part.17+0x141/0x1e0 fs/read_write.c:714
 [<ffffffff81570b10>] do_loop_readv_writev fs/read_write.c:880 [inline]
 [<ffffffff81570b10>] do_readv_writev+0x520/0x750 fs/read_write.c:874
 [<ffffffff81570dc4>] vfs_readv+0x84/0xc0 fs/read_write.c:898
 [<ffffffff8161007f>] kernel_readv fs/splice.c:363 [inline]
 [<ffffffff8161007f>] default_file_splice_read+0x43f/0x7a0 fs/splice.c:435
 [<ffffffff8160f17a>] do_splice_to+0x10a/0x160 fs/splice.c:899
 [<ffffffff8160f41d>] splice_direct_to_actor+0x24d/0x800 fs/splice.c:971
 [<ffffffff8160fb77>] do_splice_direct+0x1a7/0x270 fs/splice.c:1080
 [<ffffffff81572b8b>] do_sendfile+0x54b/0xd30 fs/read_write.c:1401
 [<ffffffff81574ae1>] SYSC_sendfile64 fs/read_write.c:1456 [inline]
 [<ffffffff81574ae1>] SyS_sendfile64+0xd1/0x160 fs/read_write.c:1448
 [<ffffffff838b34ee>] entry_SYSCALL_64_fastpath+0x29/0xe8
program syz-executor2 is using a deprecated SCSI ioctl, please convert it to SG_IO
sd 0:0:1:0: ioctl_internal_command: ILLEGAL REQUEST asc=0x20 ascq=0x0
program syz-executor2 is using a deprecated SCSI ioctl, please convert it to SG_IO
sd 0:0:1:0: ioctl_internal_command: ILLEGAL REQUEST asc=0x20 ascq=0x0
sock: sock_set_timeout: `syz-executor7' (pid 21182) tries to set negative timeout
sock: sock_set_timeout: `syz-executor7' (pid 21182) tries to set negative timeout