blk_update_request: I/O error, dev loop0, sector 0
blk_update_request: I/O error, dev loop0, sector 255

=====================================
[ BUG: bad unlock balance detected! ]
4.9.67-gf26d3c7 #106 Not tainted
-------------------------------------
syz-executor6/22391 is trying to release lock ([  169.792512] blk_update_request: I/O error, dev loop0, sector 0
blk_update_request: I/O error, dev loop0, sector 255
mrt_lock) at:
but there are no more locks to release!

other info that might help us debug this:
2 locks held by syz-executor6/22391:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815cf8df>] __fdget_pos+0x9f/0xc0 fs/file.c:781
 #1:  (&p->lock){+.+.+.}, at: [<ffffffff815e4cdd>] seq_read+0xdd/0x1290 fs/seq_file.c:178

stack backtrace:
CPU: 1 PID: 22391 Comm: syz-executor6 Not tainted 4.9.67-gf26d3c7 #106
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d67d78e8 ffffffff81d906e9 ffffffff849ae8f8 ffff8801d5a1e000
 ffffffff834dec54 ffffffff849ae8f8 ffff8801d5a1e888 ffff8801d67d7918
 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
nla_parse: 1 callbacks suppressed
netlink: 16 bytes leftover after parsing attributes in process `syz-executor3'.
netlink: 9 bytes leftover after parsing attributes in process `syz-executor3'.
A link change request failed with some changes committed already. Interface lo may have been left with an inconsistent configuration, please check.
netlink: 9 bytes leftover after parsing attributes in process `syz-executor3'.
A link change request failed with some changes committed already. Interface lo may have been left with an inconsistent configuration, please check.
sg_write: data in/out 327644/32 bytes for SCSI command 0x4-- guessing data in;
   program syz-executor2 not setting count and/or reply_len properly
device gre0 entered promiscuous mode
device gre0 left promiscuous mode
device gre0 entered promiscuous mode
device gre0 entered promiscuous mode
SELinux: unrecognized netlink message: protocol=4 nlmsg_type=4 sclass=netlink_tcpdiag_socket pig=22828 comm=syz-executor3
SELinux: unrecognized netlink message: protocol=4 nlmsg_type=4 sclass=netlink_tcpdiag_socket pig=22828 comm=syz-executor3
keychord: unsupported version 231
keychord: invalid keycode count 0
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=5120 sclass=netlink_route_socket pig=22946 comm=syz-executor3
netlink: 2 bytes leftover after parsing attributes in process `syz-executor3'.
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=5120 sclass=netlink_route_socket pig=22946 comm=syz-executor3
netlink: 2 bytes leftover after parsing attributes in process `syz-executor3'.
devpts: called with bogus options
devpts: called with bogus options
binder: 22997:22998 ERROR: BC_REGISTER_LOOPER called without request
netlink: 5 bytes leftover after parsing attributes in process `syz-executor4'.
binder: 22997:23008 got reply transaction with bad transaction stack, transaction 319 has target 22997:0
netlink: 5 bytes leftover after parsing attributes in process `syz-executor4'.
binder: 22998 RLIMIT_NICE not set
binder: 22997:23008 transaction failed 29201/-71, size 32-8 line 2938
binder: release 22997:22998 transaction 319 in, still active
binder: send failed reply for transaction 319 to 22997:23008
binder_alloc: 22997: binder_alloc_buf, no vma
binder: undelivered TRANSACTION_COMPLETE
binder: undelivered TRANSACTION_ERROR: 29201
binder: undelivered TRANSACTION_ERROR: 29189
binder: 22997:22998 ERROR: BC_REGISTER_LOOPER called without request
FAULT_FLAG_ALLOW_RETRY missing 30
CPU: 0 PID: 23026 Comm: syz-executor6 Not tainted 4.9.67-gf26d3c7 #106
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801a6fff980 ffffffff81d906e9 ffff8801a6fffc60 0000000000000000
 ffff8801c694f310 ffff8801a6fffb50 ffff8801c694f200 ffff8801a6fffb78
 ffffffff8165e307 ffffffff811c46cb ffff8801a6fffad0 00000001c517a067
Call 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
 [<ffffffff838a9985>] entry_SYSCALL_64_fastpath+0x23/0xc6
FAULT_FLAG_ALLOW_RETRY missing 30
CPU: 1 PID: 23039 Comm: syz-executor6 Not tainted 4.9.67-gf26d3c7 #106
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801c6fa7940 ffffffff81d906e9 ffff8801c6fa7c20 0000000000000000
 ffff8801c694f310 ffff8801c6fa7b10 ffff8801c694f200 ffff8801c6fa7b38
 ffffffff8165e307 0000000000000000 ffff8801c6fa7a90 00000001c517a067
Call 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
 [<ffffffff838a9985>] entry_SYSCALL_64_fastpath+0x23/0xc6
binder: 22997:23036 got reply transaction with no transaction stack
binder: 22997:23036 transaction failed 29201/-71, size 32-8 line 2923
binder: 22997:23008 transaction failed 29189/-3, size 0-0 line 3130
binder: undelivered TRANSACTION_ERROR: 29189
binder: undelivered TRANSACTION_ERROR: 29201
IPVS: Creating netns size=2536 id=35
device lo entered promiscuous mode
netlink: 8 bytes leftover after parsing attributes in process `syz-executor6'.
netlink: 8 bytes leftover after parsing attributes in process `syz-executor6'.
pktgen: kernel_thread() failed for cpu 0
pktgen: Cannot create thread for cpu 0 (-4)
pktgen: kernel_thread() failed for cpu 1
pktgen: Cannot create thread for cpu 1 (-4)
pktgen: Initialization failed for all threads
netlink: 5 bytes leftover after parsing attributes in process `syz-executor7'.
loop: Write error at byte offset 0, length 512.
blk_update_request: I/O error, dev loop4, sector 0
FAULT_FLAG_ALLOW_RETRY missing 31
loop: Write error at byte offset 0, length 512.
blk_update_request: I/O error, dev loop4, sector 0
CPU: 0 PID: 23418 Comm: syz-executor1 Not tainted 4.9.67-gf26d3c7 #106
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801a85af870 ffffffff81d906e9 ffff8801a85afb50 0000000000000000
 ffff8801c694ed10 ffff8801a85afa40 ffff8801c694ec00 ffff8801a85afa68
 ffffffff8165e307 ffff8801a85af8a0 ffffffff811b890d 0000000006e7eb40
Call 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
 [<ffffffff814cd5a2>] do_anonymous_page mm/memory.c:2783 [inline]
 [<ffffffff814cd5a2>] handle_pte_fault mm/memory.c:3488 [inline]
 [<ffffffff814cd5a2>] __handle_mm_fault mm/memory.c:3577 [inline]
 [<ffffffff814cd5a2>] handle_mm_fault+0x1f82/0x2530 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
 [<ffffffff8205c6d5>] SYSC_getrandom drivers/char/random.c:1899 [inline]
 [<ffffffff8205c6d5>] SyS_getrandom+0x165/0x2a0 drivers/char/random.c:1880
 [<ffffffff838a9985>] entry_SYSCALL_64_fastpath+0x23/0xc6