=====================================
[ BUG: bad unlock balance detected! ]
4.9.67-gf26d3c7 #106 Not tainted
-------------------------------------
syz-executor2/6620 is trying to release lock ([  178.399937] FAULT_FLAG_ALLOW_RETRY missing 30
CPU: 1 PID: 6631 Comm: syz-executor5 Not tainted 4.9.67-gf26d3c7 #106
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d938f840
 ffffffff81d906e9 ffff8801d938fb20 0000000000000000 ffff8801a51bf910
 ffff8801d938fa10 ffff8801a51bf800 ffff8801d938fa38 ffffffff8165e307
 0000000000000000 ffff8801d938f990 00000001c9332067Call Trace:
 [<ffffffff81d906e9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d906e9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff8165e307>] handle_userfault+0xa37/0x1300 fs/userfaultfd.c:323
 [<ffffffff814cd5f1>] do_anonymous_page mm/memory.c:2747 [inline]
 [<ffffffff814cd5f1>] handle_pte_fault mm/memory.c:3488 [inline]
 [<ffffffff814cd5f1>] __handle_mm_fault mm/memory.c:3577 [inline]
 [<ffffffff814cd5f1>] handle_mm_fault+0x1fd1/0x2530 mm/memory.c:3614
 [<ffffffff810dd452>] __do_page_fault+0x5c2/0xd40 arch/x86/mm/fault.c:1406
 [<ffffffff810ddbf7>] do_page_fault+0x27/0x30 arch/x86/mm/fault.c:1469
 [<ffffffff838aab58>] page_fault+0x28/0x30 arch/x86/entry/entry_64.S:1012
 [<ffffffff815e8f60>] SYSC_fsetxattr fs/xattr.c:504 [inline]
 [<ffffffff815e8f60>] SyS_fsetxattr+0x130/0x190 fs/xattr.c:493
 [<ffffffff838a9985>] entry_SYSCALL_64_fastpath+0x23/0xc6
FAULT_FLAG_ALLOW_RETRY missing 30
CPU: 1 PID: 6616 Comm: syz-executor5 Not tainted 4.9.67-gf26d3c7 #106
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d6ee75d0
 ffffffff81d906e9 ffff8801d6ee78b0 0000000000000000 ffff8801a51bf910
 ffff8801d6ee77a0 ffff8801a51bf800 ffff8801d6ee77c8 ffffffff8165e307
 0000000000005e64 ffff8801d6ee7720 00000001c9332067Call Trace:
 [<ffffffff81d906e9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d906e9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff8165e307>] handle_userfault+0xa37/0x1300 fs/userfaultfd.c:323
 [<ffffffff814cd5f1>] do_anonymous_page mm/memory.c:2747 [inline]
 [<ffffffff814cd5f1>] handle_pte_fault mm/memory.c:3488 [inline]
 [<ffffffff814cd5f1>] __handle_mm_fault mm/memory.c:3577 [inline]
 [<ffffffff814cd5f1>] handle_mm_fault+0x1fd1/0x2530 mm/memory.c:3614
 [<ffffffff810dd452>] __do_page_fault+0x5c2/0xd40 arch/x86/mm/fault.c:1406
 [<ffffffff810ddbf7>] do_page_fault+0x27/0x30 arch/x86/mm/fault.c:1469
 [<ffffffff838aab58>] page_fault+0x28/0x30 arch/x86/entry/entry_64.S:1012
 [<ffffffff815aa59a>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815aa59a>] do_vfs_ioctl+0x1aa/0x1140 fs/ioctl.c:679
 [<ffffffff815ab5bf>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<ffffffff815ab5bf>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff838a9985>] entry_SYSCALL_64_fastpath+0x23/0xc6
mrt_lock) at:
but there are no more locks to release!

other info that might help us debug this:
1 lock held by syz-executor2/6620:
 #0:  (&p->lock){+.+.+.}, at: [<ffffffff815e4cdd>] seq_read+0xdd/0x1290 fs/seq_file.c:178

stack backtrace:
CPU: 0 PID: 6620 Comm: syz-executor2 Not tainted 4.9.67-gf26d3c7 #106
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8c0f8e8 ffffffff81d906e9 ffffffff849ae8f8 ffff8801d222c800
 ffffffff834dec54 ffffffff849ae8f8 ffff8801d222d088 ffff8801d8c0f918
 ffffffff812353f4 dffffc0000000000 ffffffff849ae8f8 00000000ffffffff
Call Trace:
 [<ffffffff81d906e9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d906e9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff812353f4>] print_unlock_imbalance_bug+0x174/0x1a0 kernel/locking/lockdep.c:3398
 [<ffffffff8123dec8>] __lock_release kernel/locking/lockdep.c:3540 [inline]
 [<ffffffff8123dec8>] lock_release+0x6f8/0xb80 kernel/locking/lockdep.c:3775
 [<ffffffff838a951a>] __raw_read_unlock include/linux/rwlock_api_smp.h:225 [inline]
 [<ffffffff838a951a>] _raw_read_unlock+0x1a/0x50 kernel/locking/spinlock.c:255
 [<ffffffff834dec54>] ipmr_mfc_seq_stop+0xe4/0x140 net/ipv6/ip6mr.c:553
 [<ffffffff815e5683>] seq_read+0xa83/0x1290 fs/seq_file.c:283
 [<ffffffff816be32f>] proc_reg_read+0xef/0x170 fs/proc/inode.c:202
 [<ffffffff81568cb1>] do_loop_readv_writev.part.17+0x141/0x1e0 fs/read_write.c:714
 [<ffffffff8156cb20>] do_loop_readv_writev fs/read_write.c:880 [inline]
 [<ffffffff8156cb20>] do_readv_writev+0x520/0x750 fs/read_write.c:874
 [<ffffffff8156cdd4>] vfs_readv+0x84/0xc0 fs/read_write.c:898
 [<ffffffff8156cef6>] do_readv+0xe6/0x250 fs/read_write.c:924
 [<ffffffff815703e7>] SYSC_readv fs/read_write.c:1011 [inline]
 [<ffffffff815703e7>] SyS_readv+0x27/0x30 fs/read_write.c:1008
 [<ffffffff838a9985>] entry_SYSCALL_64_fastpath+0x23/0xc6
9pnet_virtio: no channels available for device ./file0
device gre0 entered promiscuous mode