====================================================== WARNING: possible circular locking dependency detected 4.15.0-rc2-mm1+ #39 Not tainted ------------------------------------------------------ syz-executor2/4304 is trying to acquire lock: (&tty->ldisc_sem){++++}, at: [<00000000356ea928>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 but task is already holding lock: (&pipe->mutex/1){+.+.}, at: [<000000007b4d8992>] pipe_lock_nested fs/pipe.c:67 [inline] (&pipe->mutex/1){+.+.}, at: [<000000007b4d8992>] pipe_lock+0x56/0x70 fs/pipe.c:75 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #6 (&pipe->mutex/1){+.+.}: lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4004 __mutex_lock_common kernel/locking/mutex.c:756 [inline] __mutex_lock+0x16f/0x1a80 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 pipe_lock_nested fs/pipe.c:67 [inline] pipe_lock+0x56/0x70 fs/pipe.c:75 iter_file_splice_write+0x264/0xf30 fs/splice.c:699 do_splice_from fs/splice.c:851 [inline] do_splice fs/splice.c:1147 [inline] SYSC_splice fs/splice.c:1402 [inline] SyS_splice+0x7d5/0x1630 fs/splice.c:1382 entry_SYSCALL_64_fastpath+0x1f/0x96 -> #5 (sb_writers){.+.+}: spin_lock include/linux/spinlock.h:315 [inline] devtmpfsd+0x224/0x4b0 drivers/base/devtmpfs.c:392 kthread+0x37a/0x440 kernel/kthread.c:238 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:524 0xffffffffffffffff handle_create+0x196/0x760 drivers/base/devtmpfs.c:226 -> #4 ((completion)&req.done){+.+.}: lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4004 complete_acquire include/linux/completion.h:40 [inline] __wait_for_common kernel/sched/completion.c:109 [inline] wait_for_common kernel/sched/completion.c:123 [inline] wait_for_completion+0xcb/0x7b0 kernel/sched/completion.c:144 devtmpfs_create_node+0x32b/0x4a0 drivers/base/devtmpfs.c:115 device_add+0x120f/0x1640 drivers/base/core.c:1824 device_register+0x1d/0x20 drivers/base/core.c:1905 tty_register_device_attr+0x422/0x740 drivers/tty/tty_io.c:2956 tty_port_register_device_attr_serdev+0x100/0x140 drivers/tty/tty_port.c:166 uart_add_one_port+0xa7a/0x15a0 drivers/tty/serial/serial_core.c:2783 serial8250_register_8250_port+0xfac/0x1990 drivers/tty/serial/8250/8250_core.c:1045 serial_pnp_probe+0x5e7/0xac0 drivers/tty/serial/8250/8250_pnp.c:480 pnp_device_probe+0x15f/0x250 drivers/pnp/driver.c:109 really_probe drivers/base/dd.c:424 [inline] driver_probe_device+0x71b/0xae0 drivers/base/dd.c:566 __driver_attach+0x181/0x1c0 drivers/base/dd.c:800 bus_for_each_dev+0x154/0x1e0 drivers/base/bus.c:313 driver_attach+0x3d/0x50 drivers/base/dd.c:819 bus_add_driver+0x466/0x620 drivers/base/bus.c:669 driver_register+0x1bf/0x3c0 drivers/base/driver.c:168 pnp_register_driver+0x75/0xa0 drivers/pnp/driver.c:272 serial8250_pnp_init+0x15/0x20 drivers/tty/serial/8250/8250_pnp.c:537 serial8250_init+0x8f/0x270 drivers/tty/serial/8250/8250_core.c:1122 do_one_initcall+0x9e/0x330 init/main.c:833 do_initcall_level init/main.c:899 [inline] do_initcalls init/main.c:907 [inline] do_basic_setup init/main.c:925 [inline] kernel_init_freeable+0x469/0x521 init/main.c:1073 kernel_init+0x13/0x172 init/main.c:1000 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:524 -> #3 (&port->mutex){+.+.}: lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4004 __mutex_lock_common kernel/locking/mutex.c:756 [inline] __mutex_lock+0x16f/0x1a80 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 uart_set_termios+0x8f/0x5b0 drivers/tty/serial/serial_core.c:1416 tty_set_termios+0x6d4/0xa40 drivers/tty/tty_ioctl.c:334 set_termios+0x377/0x6b0 drivers/tty/tty_ioctl.c:414 tty_mode_ioctl+0x9fb/0xb10 drivers/tty/tty_ioctl.c:749 n_tty_ioctl_helper+0x40/0x360 drivers/tty/tty_ioctl.c:940 n_tty_ioctl+0x148/0x2d0 drivers/tty/n_tty.c:2435 tty_ioctl+0x32e/0x1600 drivers/tty/tty_io.c:2638 vfs_ioctl fs/ioctl.c:46 [inline] do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:686 SYSC_ioctl fs/ioctl.c:701 [inline] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692 entry_SYSCALL_64_fastpath+0x1f/0x96 -> #2 (&tty->termios_rwsem){++++}: lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4004 down_write+0x87/0x120 kernel/locking/rwsem.c:70 n_tty_flush_buffer+0x21/0x320 drivers/tty/n_tty.c:357 tty_buffer_flush+0x29a/0x390 drivers/tty/tty_buffer.c:233 tty_ldisc_flush+0x25/0x70 drivers/tty/tty_ldisc.c:418 tty_port_close_start.part.4+0x1cd/0x4e0 drivers/tty/tty_port.c:603 tty_port_close_start drivers/tty/tty_port.c:646 [inline] tty_port_close+0x3f/0x80 drivers/tty/tty_port.c:640 uart_close+0x77/0x1d0 drivers/tty/serial/serial_core.c:1487 tty_release+0x446/0x14c0 drivers/tty/tty_io.c:1639 __fput+0x333/0x7f0 fs/file_table.c:210 ____fput+0x15/0x20 fs/file_table.c:244 task_work_run+0x199/0x270 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:191 [inline] exit_to_usermode_loop+0x275/0x2f0 arch/x86/entry/common.c:165 prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline] syscall_return_slowpath+0x490/0x550 arch/x86/entry/common.c:264 entry_SYSCALL_64_fastpath+0x94/0x96 -> #1 (&buf->lock){+.+.}: lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4004 __mutex_lock_common kernel/locking/mutex.c:756 [inline] __mutex_lock+0x16f/0x1a80 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 tty_buffer_flush+0xbd/0x390 drivers/tty/tty_buffer.c:222 tty_ldisc_flush+0x25/0x70 drivers/tty/tty_ldisc.c:418 tty_port_close_start.part.4+0x1cd/0x4e0 drivers/tty/tty_port.c:603 tty_port_close_start drivers/tty/tty_port.c:646 [inline] tty_port_close+0x3f/0x80 drivers/tty/tty_port.c:640 uart_close+0x77/0x1d0 drivers/tty/serial/serial_core.c:1487 tty_release+0x446/0x14c0 drivers/tty/tty_io.c:1639 __fput+0x333/0x7f0 fs/file_table.c:210 ____fput+0x15/0x20 fs/file_table.c:244 task_work_run+0x199/0x270 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:191 [inline] exit_to_usermode_loop+0x275/0x2f0 arch/x86/entry/common.c:165 prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline] syscall_return_slowpath+0x490/0x550 arch/x86/entry/common.c:264 entry_SYSCALL_64_fastpath+0x94/0x96 -> #0 (&tty->ldisc_sem){++++}: check_prevs_add kernel/locking/lockdep.c:2031 [inline] validate_chain kernel/locking/lockdep.c:2473 [inline] __lock_acquire+0x3498/0x47f0 kernel/locking/lockdep.c:3500 lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4004 __ldsem_down_read_nested+0xd1/0xa90 drivers/tty/tty_ldsem.c:325 ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 tty_ldisc_ref_wait+0x25/0x80 drivers/tty/tty_ldisc.c:277 tty_read+0xf8/0x250 drivers/tty/tty_io.c:852 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 do_splice fs/splice.c:1173 [inline] SYSC_splice fs/splice.c:1402 [inline] SyS_splice+0x11a8/0x1630 fs/splice.c:1382 entry_SYSCALL_64_fastpath+0x1f/0x96 other info that might help us debug this: Chain exists of: &tty->ldisc_sem --> sb_writers --> &pipe->mutex/1 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&pipe->mutex/1); lock(sb_writers); lock(&pipe->mutex/1); lock(&tty->ldisc_sem); *** DEADLOCK *** 1 lock held by syz-executor2/4304: #0: (&pipe->mutex/1){+.+.}, at: [<000000007b4d8992>] pipe_lock_nested fs/pipe.c:67 [inline] #0: (&pipe->mutex/1){+.+.}, at: [<000000007b4d8992>] pipe_lock+0x56/0x70 fs/pipe.c:75 stack backtrace: CPU: 0 PID: 4304 Comm: syz-executor2 Not tainted 4.15.0-rc2-mm1+ #39 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_circular_bug+0x42d/0x610 kernel/locking/lockdep.c:1271 check_prev_add+0x666/0x15f0 kernel/locking/lockdep.c:1914 check_prevs_add kernel/locking/lockdep.c:2031 [inline] validate_chain kernel/locking/lockdep.c:2473 [inline] __lock_acquire+0x3498/0x47f0 kernel/locking/lockdep.c:3500 lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4004 __ldsem_down_read_nested+0xd1/0xa90 drivers/tty/tty_ldsem.c:325 ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 tty_ldisc_ref_wait+0x25/0x80 drivers/tty/tty_ldisc.c:277 tty_read+0xf8/0x250 drivers/tty/tty_io.c:852 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 do_splice fs/splice.c:1173 [inline] SYSC_splice fs/splice.c:1402 [inline] SyS_splice+0x11a8/0x1630 fs/splice.c:1382 entry_SYSCALL_64_fastpath+0x1f/0x96 RIP: 0033:0x452a09 RSP: 002b:00007f6f62ff9c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000113 RAX: ffffffffffffffda RBX: 00007f6f62ffa700 RCX: 0000000000452a09 RDX: 0000000000000015 RSI: 0000000000000000 RDI: 0000000000000013 RBP: 0000000000000000 R08: 0000000000000200 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000212 R12: 0000000000000000 R13: 0000000000a2f7ff R14: 00007f6f62ffa9c0 R15: 0000000000000000 netlink: 6 bytes leftover after parsing attributes in process `syz-executor4'. IPv6: Can't replace route, no match found IPv6: Can't replace route, no match found rfkill: input handler disabled rfkill: input handler enabled audit: type=1326 audit(1513584868.473:50): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 pid=4202 comm="syz-executor2" exe="/root/syz-executor2" sig=0 arch=c000003e syscall=202 compat=0 ip=0x452a09 code=0x7ffc0000 audit: type=1326 audit(1513584868.473:51): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 pid=4202 comm="syz-executor2" exe="/root/syz-executor2" sig=0 arch=c000003e syscall=41 compat=0 ip=0x452a09 code=0x7ffc0000 audit: type=1326 audit(1513584868.474:52): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 pid=4202 comm="syz-executor2" exe="/root/syz-executor2" sig=0 arch=c000003e syscall=202 compat=0 ip=0x452a09 code=0x7ffc0000 audit: type=1326 audit(1513584868.474:53): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 pid=4202 comm="syz-executor2" exe="/root/syz-executor2" sig=0 arch=c000003e syscall=173 compat=0 ip=0x452a09 code=0x7ffc0000 audit: type=1326 audit(1513584868.475:54): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 pid=4202 comm="syz-executor2" exe="/root/syz-executor2" sig=0 arch=c000003e syscall=202 compat=0 ip=0x452a09 code=0x7ffc0000 device gre0 entered promiscuous mode nla_parse: 3 callbacks suppressed netlink: 3 bytes leftover after parsing attributes in process `syz-executor1'. netlink: 3 bytes leftover after parsing attributes in process `syz-executor1'. sctp: [Deprecated]: syz-executor1 (pid 4562) Use of int in maxseg socket option. Use struct sctp_assoc_value instead Subscription rejected, illegal request sctp: [Deprecated]: syz-executor1 (pid 4562) Use of int in maxseg socket option. Use struct sctp_assoc_value instead Subscription rejected, illegal request SELinux: unrecognized netlink message: protocol=0 nlmsg_type=9472 sclass=netlink_route_socket pig=4618 comm=syz-executor1 SELinux: unrecognized netlink message: protocol=0 nlmsg_type=9472 sclass=netlink_route_socket pig=4618 comm=syz-executor1 sctp: [Deprecated]: syz-executor2 (pid 4759) Use of int in maxseg socket option. Use struct sctp_assoc_value instead sctp: [Deprecated]: syz-executor2 (pid 4759) Use of int in maxseg socket option. Use struct sctp_assoc_value instead netlink: 3 bytes leftover after parsing attributes in process `syz-executor0'. netlink: 3 bytes leftover after parsing attributes in process `syz-executor0'. sock: sock_set_timeout: `syz-executor3' (pid 4791) tries to set negative timeout sock: sock_set_timeout: `syz-executor3' (pid 4791) tries to set negative timeout device gre0 entered promiscuous mode kauditd_printk_skb: 266 callbacks suppressed audit: type=1400 audit(1513584872.052:321): avc: denied { getopt } for pid=4932 comm="syz-executor1" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_generic_socket permissive=1 audit: type=1326 audit(1513584872.089:322): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 pid=4881 comm="syz-executor7" exe="/root/syz-executor7" sig=0 arch=c000003e syscall=321 compat=0 ip=0x452a09 code=0x7ffc0000 audit: type=1326 audit(1513584872.089:323): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 pid=4881 comm="syz-executor7" exe="/root/syz-executor7" sig=0 arch=c000003e syscall=202 compat=0 ip=0x452a09 code=0x7ffc0000 audit: type=1326 audit(1513584872.089:324): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 pid=4881 comm="syz-executor7" exe="/root/syz-executor7" sig=0 arch=c000003e syscall=202 compat=0 ip=0x452a09 code=0x7ffc0000 audit: type=1326 audit(1513584872.093:325): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 pid=4881 comm="syz-executor7" exe="/root/syz-executor7" sig=0 arch=c000003e syscall=1 compat=0 ip=0x452a09 code=0x7ffc0000 audit: type=1326 audit(1513584872.093:326): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 pid=4881 comm="syz-executor7" exe="/root/syz-executor7" sig=0 arch=c000003e syscall=202 compat=0 ip=0x452a09 code=0x7ffc0000 audit: type=1326 audit(1513584872.093:327): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 pid=4881 comm="syz-executor7" exe="/root/syz-executor7" sig=0 arch=c000003e syscall=202 compat=0 ip=0x452a09 code=0x7ffc0000 DRBG: could not allocate digest TFM handle: hmac(sha256) DRBG: could not allocate digest TFM handle: hmac(sha256) audit: type=1326 audit(1513584872.097:328): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 pid=4881 comm="syz-executor7" exe="/root/syz-executor7" sig=0 arch=c000003e syscall=257 compat=0 ip=0x452a09 code=0x7ffc0000 netlink: 9 bytes leftover after parsing attributes in process `syz-executor2'. A link change request failed with some changes committed already. Interface lo may have been left with an inconsistent configuration, please check. DRBG: could not allocate CTR cipher TFM handle: ctr(aes) netlink: 9 bytes leftover after parsing attributes in process `syz-executor2'. A link change request failed with some changes committed already. Interface lo may have been left with an inconsistent configuration, please check. netlink: 17 bytes leftover after parsing attributes in process `syz-executor0'. netlink: 17 bytes leftover after parsing attributes in process `syz-executor0'. netlink: 3 bytes leftover after parsing attributes in process `syz-executor7'. netlink: 3 bytes leftover after parsing attributes in process `syz-executor7'. QAT: Invalid ioctl QAT: Invalid ioctl QAT: Invalid ioctl QAT: Invalid ioctl QAT: Invalid ioctl QAT: Invalid ioctl audit: type=1326 audit(1513584872.097:329): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 pid=4881 comm="syz-executor7" exe="/root/syz-executor7" sig=0 arch=c000003e syscall=202 compat=0 ip=0x452a09 code=0x7ffc0000 audit: type=1326 audit(1513584872.097:330): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 pid=4881 comm="syz-executor7" exe="/root/syz-executor7" sig=0 arch=c000003e syscall=202 compat=0 ip=0x452a09 code=0x7ffc0000 dccp_close: ABORT with 152 bytes unread device lo entered promiscuous mode QAT: Invalid ioctl device eql entered promiscuous mode SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket pig=5568 comm=syz-executor4 device lo entered promiscuous mode SELinux: unrecognized netlink message: protocol=6 nlmsg_type=1796 sclass=netlink_xfrm_socket pig=5814 comm=syz-executor3 device gre0 entered promiscuous mode FAULT_INJECTION: forcing a failure. name failslab, interval 1, probability 0, space 0, times 1 CPU: 1 PID: 5987 Comm: syz-executor2 Not tainted 4.15.0-rc2-mm1+ #39 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 fail_dump lib/fault-inject.c:51 [inline] should_fail+0x8c0/0xa40 lib/fault-inject.c:149 should_failslab+0xec/0x120 mm/failslab.c:32 slab_pre_alloc_hook mm/slab.h:425 [inline] slab_alloc mm/slab.c:3372 [inline] kmem_cache_alloc+0x47/0x760 mm/slab.c:3546 dst_alloc+0x11f/0x1a0 net/core/dst.c:104 rt_dst_alloc+0xe9/0x520 net/ipv4/route.c:1500 __mkroute_output net/ipv4/route.c:2242 [inline] ip_route_output_key_hash_rcu+0xa40/0x2c10 net/ipv4/route.c:2470 ip_route_output_key_hash+0x20b/0x370 net/ipv4/route.c:2299 __ip_route_output_key include/net/route.h:125 [inline] ip_route_output_flow+0x26/0xa0 net/ipv4/route.c:2553 raw_sendmsg+0xc1b/0x1fe0 net/ipv4/raw.c:633 inet_sendmsg+0x11f/0x5e0 net/ipv4/af_inet.c:763 sock_sendmsg_nosec net/socket.c:636 [inline] sock_sendmsg+0xca/0x110 net/socket.c:646 SYSC_sendto+0x358/0x5a0 net/socket.c:1727 SyS_sendto+0x40/0x50 net/socket.c:1695 entry_SYSCALL_64_fastpath+0x1f/0x96 RIP: 0033:0x452a09 RSP: 002b:00007f6f62ff9c58 EFLAGS: 00000212 ORIG_RAX: 000000000000002c RAX: ffffffffffffffda RBX: 00007f6f62ff9aa0 RCX: 0000000000452a09 RDX: 0000000000000000 RSI: 0000000020000f86 RDI: 0000000000000014 RBP: 00007f6f62ff9a90 R08: 0000000020002000 R09: 0000000000000010 R10: 0000000000000810 R11: 0000000000000212 R12: 00000000004b75bb R13: 00007f6f62ff9bc8 R14: 00000000004b75bb R15: 0000000000000000 device gre0 entered promiscuous mode device gre0 entered promiscuous mode SELinux: unrecognized netlink message: protocol=0 nlmsg_type=9472 sclass=netlink_route_socket pig=6081 comm=syz-executor3 SELinux: unrecognized netlink message: protocol=0 nlmsg_type=9472 sclass=netlink_route_socket pig=6081 comm=syz-executor3 QAT: Invalid ioctl QAT: Invalid ioctl QAT: Invalid ioctl QAT: Invalid ioctl QAT: Invalid ioctl QAT: Invalid ioctl kvm: apic: phys broadcast and lowest prio device gre0 entered promiscuous mode print_req_error: I/O error, dev loop4, sector 0 Buffer I/O error on dev loop4, logical block 0, lost async page write