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frostschutz opened this issue Nov 27, 2019 · 6 comments
Closed

losetup /dev/loopX int overflow for large X #903

frostschutz opened this issue Nov 27, 2019 · 6 comments
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@frostschutz
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This might be exclusively a kernel bug, or losetup, or both, not sure. I report it here because losetup is the trigger.

Out of curiosity I tried to experimentally determine what the largest /dev/loop# number might be.

# losetup /dev/loop1048576 somefile

This actually seem to try to create /dev/loop0 instead, and if already exists:

kobject_add_internal failed for 7:0 with -EEXIST, don't try to register things with the same name in the same directory.
kobject_add_internal failed for integrity (error: -2 parent: loop1048576)

Same thing happens when trying to create /dev/loop1048575 and /dev/loop2097151, and it's not possible to remove /dev/loop1048575 afterwards.

# losetup
/dev/loop1048575 [...]
# losetup -D
losetup: /dev/loop1048575: detach failed: No such device or address.

See also: full dmesg.txt
@karelzak karelzak added the NEEDINFO Need more information from reporter label Dec 3, 2019
@karelzak
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karelzak commented Dec 3, 2019

It works for me (version 2.33.2 as well as the current upstream tree) on kernel 5.4.0-0.rc8.git0.2.fc32.x86_64:

# losetup /dev/loop1048576 somefile
# losetup
NAME             SIZELIMIT OFFSET AUTOCLEAR RO BACK-FILE                                     DIO LOG-SEC
/dev/loop1048576         0      0         0  0 /home/projects/util-linux/util-linux/somefile   0     512
# losetup -D

Please, try "LOOPDEV_DEBUG=all losetup /dev/loop1048576 somefile" to get more details.

Anyway, the dmesg output seems like a kernel problem.

@frostschutz
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Setup:

[root@KVM-NEU ~]# uname -a
Linux KVM-NEU 5.4.1-arch1-1 #1 SMP PREEMPT Fri, 29 Nov 2019 13:37:24 +0000 x86_64 GNU/Linux
[root@KVM-NEU ~]# truncate -s 1M somefile
[root@KVM-NEU ~]# export LOOPDEV_DEBUG=all
[root@KVM-NEU ~]# losetup /dev/loop0 somefile
432: loopdev:      CXT: [0x7ffc52078140]: initialize context
432: loopdev:      CXT: [0x7ffc52078140]: init: ignore ioctls
432: loopdev:      CXT: [0x7ffc52078140]: init: loop-control detected 
432: loopdev:      CXT: [0x7ffc52078140]: /dev/loop0 name assigned
432: loopdev:      CXT: [0x7ffc52078140]: add_device 0
432: loopdev:      CXT: [0x7ffc52078140]: add_device done [rc=-1]
432: loopdev:      CXT: [0x7ffc52078140]: set backing file=/root/somefile
432: loopdev:    SETUP: [0x7ffc52078140]: device setup requested
432: loopdev:    SETUP: [0x7ffc52078140]: backing file open: OK
432: loopdev:      CXT: [0x7ffc52078140]: open /dev/loop0 [rw]: Success
432: loopdev:    SETUP: [0x7ffc52078140]: device open: OK
432: loopdev:    SETUP: [0x7ffc52078140]: LOOP_SET_FD: OK
432: loopdev:    SETUP: [0x7ffc52078140]: LOOP_SET_STATUS64: OK
432: loopdev:    SETUP: [0x7ffc52078140]: success [rc=0]
432: loopdev:      CXT: [0x7ffc52078140]: de-initialize
432: loopdev:      CXT: [0x7ffc52078140]: closing old open fd
432: loopdev:     ITER: [0x7ffc520782d0]: de-initialize
[root@KVM-NEU ~]# losetup /dev/loop1048576 somefile
444: loopdev:      CXT: [0x7ffd08568400]: initialize context
444: loopdev:      CXT: [0x7ffd08568400]: init: ignore ioctls
444: loopdev:      CXT: [0x7ffd08568400]: init: loop-control detected 
444: loopdev:      CXT: [0x7ffd08568400]: /dev/loop1048576 name assigned
444: loopdev:      CXT: [0x7ffd08568400]: add_device 1048576
444: loopdev:      CXT: [0x7ffd08568400]: add_device done [rc=1048576]
444: loopdev:      CXT: [0x7ffd08568400]: set backing file=/root/somefile
444: loopdev:    SETUP: [0x7ffd08568400]: device setup requested
444: loopdev:    SETUP: [0x7ffd08568400]: backing file open: OK
444: loopdev:      CXT: [0x7ffd08568400]: open /dev/loop1048576 [rw]: No such file or directory
444: loopdev:      CXT: [0x7ffd08568400]: open /dev/loop1048576 [rw]: No such file or directory
444: loopdev:      CXT: [0x7ffd08568400]: open /dev/loop1048576 [rw]: No such file or directory
444: loopdev:      CXT: [0x7ffd08568400]: open /dev/loop1048576 [rw]: No such file or directory
444: loopdev:      CXT: [0x7ffd08568400]: open /dev/loop1048576 [rw]: No such file or directory
444: loopdev:      CXT: [0x7ffd08568400]: open /dev/loop1048576 [rw]: No such file or directory
444: loopdev:      CXT: [0x7ffd08568400]: open /dev/loop1048576 [rw]: No such file or directory
444: loopdev:      CXT: [0x7ffd08568400]: open /dev/loop1048576 [rw]: No such file or directory
444: loopdev:      CXT: [0x7ffd08568400]: open /dev/loop1048576 [rw]: No such file or directory
444: loopdev:      CXT: [0x7ffd08568400]: open /dev/loop1048576 [rw]: No such file or directory
444: loopdev:      CXT: [0x7ffd08568400]: open /dev/loop1048576 [rw]: No such file or directory
444: loopdev:      CXT: [0x7ffd08568400]: open /dev/loop1048576 [rw]: No such file or directory
444: loopdev:      CXT: [0x7ffd08568400]: open /dev/loop1048576 [rw]: No such file or directory
444: loopdev:      CXT: [0x7ffd08568400]: open /dev/loop1048576 [rw]: No such file or directory
444: loopdev:      CXT: [0x7ffd08568400]: open /dev/loop1048576 [rw]: No such file or directory
444: loopdev:      CXT: [0x7ffd08568400]: open /dev/loop1048576 [rw]: No such file or directory
444: loopdev:      CXT: [0x7ffd08568400]: open /dev/loop1048576 [rw]: No such file or directory
444: loopdev:    SETUP: [0x7ffd08568400]: failed [rc=-2]
444: loopdev:      CXT: [0x7ffd08568400]: open /dev/loop1048576 [rw]: No such file or directory
losetup: /dev/loop1048576: failed to set up loop device: No such file or directory
444: loopdev:      CXT: [0x7ffd08568400]: de-initialize
444: loopdev:     ITER: [0x7ffd08568590]: de-initialize

Setup dmesg:

[  112.660308] sysfs: cannot create duplicate filename '/devices/virtual/bdi/7:0'
[  112.660325] CPU: 0 PID: 444 Comm: losetup Not tainted 5.4.1-arch1-1 #1
[  112.660326] Hardware name: netcup KVM Server, BIOS VPS 200 G8 12/02/2019
[  112.660332] Call Trace:
[  112.660426]  dump_stack+0x66/0x90
[  112.660447]  sysfs_warn_dup.cold+0x17/0x2d
[  112.660456]  sysfs_create_dir_ns+0xc6/0xe0
[  112.660459]  kobject_add_internal+0xab/0x290
[  112.660465]  kobject_add+0x98/0xd0
[  112.660480]  ? preempt_count_add+0x68/0xa0
[  112.660495]  device_add+0x123/0x6b0
[  112.660504]  device_create_groups_vargs+0xd3/0xf0
[  112.660506]  device_create_vargs+0x12/0x20
[  112.660517]  bdi_register_va.part.0+0x23/0x200
[  112.660526]  bdi_register+0x79/0x80
[  112.660528]  bdi_register_owner+0x2c/0x60
[  112.660540]  __device_add_disk+0x440/0x4b0
[  112.660575]  loop_add+0x1e4/0x250 [loop]
[  112.660580]  loop_control_ioctl+0xa7/0x140 [loop]
[  112.660592]  do_vfs_ioctl+0x43d/0x6c0
[  112.660614]  ? syscall_trace_enter+0x19c/0x2e0
[  112.660616]  ksys_ioctl+0x5e/0x90
[  112.660618]  __x64_sys_ioctl+0x16/0x20
[  112.660620]  do_syscall_64+0x4e/0x140
[  112.660634]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[  112.660650] RIP: 0033:0x7f9b251ea25b
[  112.660656] Code: 0f 1e fa 48 8b 05 25 9c 0c 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d f5 9b 0c 00 f7 d8 64 89 01 48
[  112.660657] RSP: 002b:00007ffd08568338 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
[  112.660659] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f9b251ea25b
[  112.660659] RDX: 0000000000100000 RSI: 0000000000004c80 RDI: 0000000000000003
[  112.660660] RBP: 00007ffd08568400 R08: 000000000000000a R09: 0000000000000012
[  112.660661] R10: 00007ffd08565b31 R11: 0000000000000246 R12: 0000000000000003
[  112.660661] R13: 00007ffd08568344 R14: 000055a4a27d4020 R15: 00007ffd08568400
[  112.660664] kobject_add_internal failed for 7:0 with -EEXIST, don't try to register things with the same name in the same directory.
[  112.660714] ------------[ cut here ]------------
[  112.660730] WARNING: CPU: 0 PID: 444 at block/genhd.c:741 __device_add_disk+0x4a2/0x4b0
[  112.660732] Modules linked in: loop cfg80211 rfkill 8021q garp mrp stp llc cirrus drm_kms_helper drm psmouse joydev input_leds mousedev intel_agp pcspkr i6300esb syscopyarea intel_gtt sysfillrect evdev sysimgblt agpgart qemu_fw_cfg mac_hid fb_sys_fops i2c_piix4 ip_tables x_tables ext4 crc32c_generic crc16 mbcache jbd2 dm_crypt dm_mod hid_generic usbhid hid sd_mod sr_mod cdrom ata_generic pata_acpi virtio_balloon virtio_scsi virtio_console ata_piix serio_raw atkbd libps2 libata crct10dif_pclmul crc32_pclmul uhci_hcd crc32c_intel ehci_pci ghash_clmulni_intel scsi_mod virtio_pci ehci_hcd floppy i8042 serio virtio_net net_failover failover aesni_intel crypto_simd cryptd glue_helper
[  112.660787] CPU: 0 PID: 444 Comm: losetup Not tainted 5.4.1-arch1-1 #1
[  112.660787] Hardware name: netcup KVM Server, BIOS VPS 200 G8 12/02/2019
[  112.660789] RIP: 0010:__device_add_disk+0x4a2/0x4b0
[  112.660791] Code: 74 da fe ff e9 ee fd ff ff 80 a5 ac 00 00 00 ef e9 da fd ff ff 0f 0b e9 d3 fd ff ff 0f 0b e9 e8 fd ff ff 0f 0b e9 9c fc ff ff <0f> 0b eb 9e e8 25 d8 c6 ff 0f 1f 44 00 00 0f 1f 44 00 00 b9 01 00
[  112.660791] RSP: 0018:ffffb35240293db0 EFLAGS: 00010282
[  112.660793] RAX: 00000000ffffffef RBX: 0000000000000001 RCX: 0000000000000000
[  112.660793] RDX: ffffb35240293d30 RSI: ffff9feebda2f040 RDI: 000000000002f040
[  112.660794] RBP: ffff9feebb5e4000 R08: 0000000000000233 R09: 0000000000000001
[  112.660795] R10: 0000000000000286 R11: 0000000000000001 R12: ffff9feebb5e4070
[  112.660795] R13: ffff9feebb5e400c R14: 0000000000000000 R15: 0000000000000000
[  112.660797] FS:  00007f9b250f1740(0000) GS:ffff9feebda00000(0000) knlGS:0000000000000000
[  112.660797] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  112.660798] CR2: 00007f9b251da4e0 CR3: 000000007b6b2004 CR4: 00000000000606f0
[  112.660801] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  112.660801] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  112.660802] Call Trace:
[  112.660806]  loop_add+0x1e4/0x250 [loop]
[  112.660808]  loop_control_ioctl+0xa7/0x140 [loop]
[  112.660810]  do_vfs_ioctl+0x43d/0x6c0
[  112.660812]  ? syscall_trace_enter+0x19c/0x2e0
[  112.660813]  ksys_ioctl+0x5e/0x90
[  112.660815]  __x64_sys_ioctl+0x16/0x20
[  112.660816]  do_syscall_64+0x4e/0x140
[  112.660818]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[  112.660819] RIP: 0033:0x7f9b251ea25b
[  112.660820] Code: 0f 1e fa 48 8b 05 25 9c 0c 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d f5 9b 0c 00 f7 d8 64 89 01 48
[  112.660821] RSP: 002b:00007ffd08568338 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
[  112.660821] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f9b251ea25b
[  112.660822] RDX: 0000000000100000 RSI: 0000000000004c80 RDI: 0000000000000003
[  112.660823] RBP: 00007ffd08568400 R08: 000000000000000a R09: 0000000000000012
[  112.660823] R10: 00007ffd08565b31 R11: 0000000000000246 R12: 0000000000000003
[  112.660824] R13: 00007ffd08568344 R14: 000055a4a27d4020 R15: 00007ffd08568400
[  112.660826] ---[ end trace 1f3c07c7bf2ac599 ]---
[  112.660971] sysfs: cannot create duplicate filename '/dev/block/7:0'
[  112.660973] CPU: 0 PID: 444 Comm: losetup Tainted: G        W         5.4.1-arch1-1 #1
[  112.660974] Hardware name: netcup KVM Server, BIOS VPS 200 G8 12/02/2019
[  112.660974] Call Trace:
[  112.660978]  dump_stack+0x66/0x90
[  112.660980]  sysfs_warn_dup.cold+0x17/0x2d
[  112.660982]  sysfs_do_create_link_sd.isra.0+0xbe/0xd0
[  112.660985]  device_add+0x5ff/0x6b0
[  112.660988]  __device_add_disk+0x14d/0x4b0
[  112.660991]  loop_add+0x1e4/0x250 [loop]
[  112.660994]  loop_control_ioctl+0xa7/0x140 [loop]
[  112.660996]  do_vfs_ioctl+0x43d/0x6c0
[  112.661000]  ? syscall_trace_enter+0x19c/0x2e0
[  112.661002]  ksys_ioctl+0x5e/0x90
[  112.661004]  __x64_sys_ioctl+0x16/0x20
[  112.661007]  do_syscall_64+0x4e/0x140
[  112.661009]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[  112.661015] RIP: 0033:0x7f9b251ea25b
[  112.661017] Code: 0f 1e fa 48 8b 05 25 9c 0c 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d f5 9b 0c 00 f7 d8 64 89 01 48
[  112.661018] RSP: 002b:00007ffd08568338 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
[  112.661020] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f9b251ea25b
[  112.661021] RDX: 0000000000100000 RSI: 0000000000004c80 RDI: 0000000000000003
[  112.661022] RBP: 00007ffd08568400 R08: 000000000000000a R09: 0000000000000012
[  112.661023] R10: 00007ffd08565b31 R11: 0000000000000246 R12: 0000000000000003
[  112.661025] R13: 00007ffd08568344 R14: 000055a4a27d4020 R15: 00007ffd08568400
[  112.661079] ------------[ cut here ]------------
[  112.661083] WARNING: CPU: 0 PID: 444 at fs/sysfs/group.c:115 internal_create_group+0x363/0x390
[  112.661083] Modules linked in: loop cfg80211 rfkill 8021q garp mrp stp llc cirrus drm_kms_helper drm psmouse joydev input_leds mousedev intel_agp pcspkr i6300esb syscopyarea intel_gtt sysfillrect evdev sysimgblt agpgart qemu_fw_cfg mac_hid fb_sys_fops i2c_piix4 ip_tables x_tables ext4 crc32c_generic crc16 mbcache jbd2 dm_crypt dm_mod hid_generic usbhid hid sd_mod sr_mod cdrom ata_generic pata_acpi virtio_balloon virtio_scsi virtio_console ata_piix serio_raw atkbd libps2 libata crct10dif_pclmul crc32_pclmul uhci_hcd crc32c_intel ehci_pci ghash_clmulni_intel scsi_mod virtio_pci ehci_hcd floppy i8042 serio virtio_net net_failover failover aesni_intel crypto_simd cryptd glue_helper
[  112.661133] CPU: 0 PID: 444 Comm: losetup Tainted: G        W         5.4.1-arch1-1 #1
[  112.661134] Hardware name: netcup KVM Server, BIOS VPS 200 G8 12/02/2019
[  112.661135] RIP: 0010:internal_create_group+0x363/0x390
[  112.661137] Code: e8 d2 cf ff ff 8b 04 24 e9 db fe ff ff 49 8b 6c 24 30 e9 54 fd ff ff 48 85 c0 0f 85 01 fd ff ff b8 ea ff ff ff e9 e3 fe ff ff <0f> 0b b8 ea ff ff ff e9 d7 fe ff ff 49 8b 7c 24 30 48 8b 33 e8 84
[  112.661137] RSP: 0018:ffffb35240293d18 EFLAGS: 00010246
[  112.661138] RAX: 0000000000000000 RBX: ffffffffa2466ce0 RCX: 0000000000000000
[  112.661139] RDX: ffffffffa2466ce0 RSI: 0000000000000000 RDI: ffff9feebb5e4070
[  112.661140] RBP: ffff9feebb5e4070 R08: ffffffffa2543ae0 R09: 0000000000000001
[  112.661141] R10: 0000000000000023 R11: ffff9feebc532200 R12: ffff9feebb5e4070
[  112.661142] R13: ffff9feebb5e400c R14: 0000000000000000 R15: ffff9fee76507310
[  112.661144] FS:  00007f9b250f1740(0000) GS:ffff9feebda00000(0000) knlGS:0000000000000000
[  112.661145] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  112.661146] CR2: 00007f9b251da4e0 CR3: 000000007b6b2004 CR4: 00000000000606f0
[  112.661149] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  112.661150] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  112.661151] Call Trace:
[  112.661162]  blk_register_queue+0x4b/0x230
[  112.661173]  __device_add_disk+0x47c/0x4b0
[  112.661177]  loop_add+0x1e4/0x250 [loop]
[  112.661180]  loop_control_ioctl+0xa7/0x140 [loop]
[  112.661183]  do_vfs_ioctl+0x43d/0x6c0
[  112.661186]  ? syscall_trace_enter+0x19c/0x2e0
[  112.661188]  ksys_ioctl+0x5e/0x90
[  112.661191]  __x64_sys_ioctl+0x16/0x20
[  112.661193]  do_syscall_64+0x4e/0x140
[  112.661195]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[  112.661196] RIP: 0033:0x7f9b251ea25b
[  112.661198] Code: 0f 1e fa 48 8b 05 25 9c 0c 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d f5 9b 0c 00 f7 d8 64 89 01 48
[  112.661198] RSP: 002b:00007ffd08568338 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
[  112.661199] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f9b251ea25b
[  112.661200] RDX: 0000000000100000 RSI: 0000000000004c80 RDI: 0000000000000003
[  112.661200] RBP: 00007ffd08568400 R08: 000000000000000a R09: 0000000000000012
[  112.661204] R10: 00007ffd08565b31 R11: 0000000000000246 R12: 0000000000000003
[  112.661205] R13: 00007ffd08568344 R14: 000055a4a27d4020 R15: 00007ffd08568400
[  112.661207] ---[ end trace 1f3c07c7bf2ac59a ]---
[  112.664554] ------------[ cut here ]------------
[  112.664566] WARNING: CPU: 0 PID: 444 at fs/sysfs/file.c:327 sysfs_create_file_ns+0x8b/0xa0
[  112.664566] Modules linked in: loop cfg80211 rfkill 8021q garp mrp stp llc cirrus drm_kms_helper drm psmouse joydev input_leds mousedev intel_agp pcspkr i6300esb syscopyarea intel_gtt sysfillrect evdev sysimgblt agpgart qemu_fw_cfg mac_hid fb_sys_fops i2c_piix4 ip_tables x_tables ext4 crc32c_generic crc16 mbcache jbd2 dm_crypt dm_mod hid_generic usbhid hid sd_mod sr_mod cdrom ata_generic pata_acpi virtio_balloon virtio_scsi virtio_console ata_piix serio_raw atkbd libps2 libata crct10dif_pclmul crc32_pclmul uhci_hcd crc32c_intel ehci_pci ghash_clmulni_intel scsi_mod virtio_pci ehci_hcd floppy i8042 serio virtio_net net_failover failover aesni_intel crypto_simd cryptd glue_helper
[  112.664595] CPU: 0 PID: 444 Comm: losetup Tainted: G        W         5.4.1-arch1-1 #1
[  112.664595] Hardware name: netcup KVM Server, BIOS VPS 200 G8 12/02/2019
[  112.664597] RIP: 0010:sysfs_create_file_ns+0x8b/0xa0
[  112.664599] Code: 4c 24 0c 48 89 ee 44 8b 44 24 08 e8 0f fe ff ff 5a 48 8b 4c 24 08 65 48 33 0c 25 28 00 00 00 75 12 48 83 c4 10 5b 5d 41 5c c3 <0f> 0b b8 ea ff ff ff eb de e8 97 68 d3 ff 0f 1f 80 00 00 00 00 0f
[  112.664600] RSP: 0018:ffffb35240293d58 EFLAGS: 00010246
[  112.664601] RAX: 0000000000000000 RBX: ffff9feebb5e4070 RCX: 0000000000000000
[  112.664602] RDX: 0000000000000000 RSI: ffffffffa2065d20 RDI: ffff9feebb5e4070
[  112.664602] RBP: ffffffffa24aef80 R08: ffffffffa2543ae0 R09: 0000000000000001
[  112.664603] R10: 0000000000000023 R11: ffff9feebc532200 R12: ffff9feebb5e4070
[  112.664604] R13: ffff9feebb5e4070 R14: 0000000000000000 R15: 0000000000000000
[  112.664605] FS:  00007f9b250f1740(0000) GS:ffff9feebda00000(0000) knlGS:0000000000000000
[  112.664605] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  112.664606] CR2: 00007f1632bff810 CR3: 000000007b6b2004 CR4: 00000000000606f0
[  112.664609] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  112.664610] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  112.664610] Call Trace:
[  112.664615]  sysfs_create_files+0x2c/0x90
[  112.664618]  __device_add_disk+0x292/0x4b0
[  112.664623]  loop_add+0x1e4/0x250 [loop]
[  112.664626]  loop_control_ioctl+0xa7/0x140 [loop]
[  112.664628]  do_vfs_ioctl+0x43d/0x6c0
[  112.664633]  ? syscall_trace_enter+0x19c/0x2e0
[  112.664635]  ksys_ioctl+0x5e/0x90
[  112.664637]  __x64_sys_ioctl+0x16/0x20
[  112.664639]  do_syscall_64+0x4e/0x140
[  112.664642]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[  112.664645] RIP: 0033:0x7f9b251ea25b
[  112.664647] Code: 0f 1e fa 48 8b 05 25 9c 0c 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d f5 9b 0c 00 f7 d8 64 89 01 48
[  112.664648] RSP: 002b:00007ffd08568338 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
[  112.664650] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f9b251ea25b
[  112.664651] RDX: 0000000000100000 RSI: 0000000000004c80 RDI: 0000000000000003
[  112.664652] RBP: 00007ffd08568400 R08: 000000000000000a R09: 0000000000000012
[  112.664652] R10: 00007ffd08565b31 R11: 0000000000000246 R12: 0000000000000003
[  112.664653] R13: 00007ffd08568344 R14: 000055a4a27d4020 R15: 00007ffd08568400
[  112.664656] ---[ end trace 1f3c07c7bf2ac59b ]---
[  112.664658] ------------[ cut here ]------------
[  112.664658] kernfs: can not remove 'events', no directory
[  112.664671] WARNING: CPU: 0 PID: 444 at fs/kernfs/dir.c:1504 kernfs_remove_by_name_ns+0x83/0x90
[  112.664671] Modules linked in: loop cfg80211 rfkill 8021q garp mrp stp llc cirrus drm_kms_helper drm psmouse joydev input_leds mousedev intel_agp pcspkr i6300esb syscopyarea intel_gtt sysfillrect evdev sysimgblt agpgart qemu_fw_cfg mac_hid fb_sys_fops i2c_piix4 ip_tables x_tables ext4 crc32c_generic crc16 mbcache jbd2 dm_crypt dm_mod hid_generic usbhid hid sd_mod sr_mod cdrom ata_generic pata_acpi virtio_balloon virtio_scsi virtio_console ata_piix serio_raw atkbd libps2 libata crct10dif_pclmul crc32_pclmul uhci_hcd crc32c_intel ehci_pci ghash_clmulni_intel scsi_mod virtio_pci ehci_hcd floppy i8042 serio virtio_net net_failover failover aesni_intel crypto_simd cryptd glue_helper
[  112.664702] CPU: 0 PID: 444 Comm: losetup Tainted: G        W         5.4.1-arch1-1 #1
[  112.664703] Hardware name: netcup KVM Server, BIOS VPS 200 G8 12/02/2019
[  112.664706] RIP: 0010:kernfs_remove_by_name_ns+0x83/0x90
[  112.664707] Code: 5a 5d 00 31 c0 5d 41 5c 41 5d c3 48 c7 c7 c0 b3 49 a2 e8 60 5a 5d 00 b8 fe ff ff ff eb e7 48 c7 c7 d8 96 2f a2 e8 7b 89 d3 ff <0f> 0b b8 fe ff ff ff eb d2 0f 1f 40 00 0f 1f 44 00 00 41 57 41 56
[  112.664708] RSP: 0018:ffffb35240293d68 EFLAGS: 00010286
[  112.664709] RAX: 0000000000000000 RBX: ffffffffa24aef78 RCX: 0000000000000000
[  112.664710] RDX: 0000000000000001 RSI: 0000000000000086 RDI: 00000000ffffffff
[  112.664711] RBP: ffffffffa24aef78 R08: 00000000000002be R09: 0000000000000001
[  112.664713] R10: 0000000000000000 R11: 0000000000000001 R12: ffffffffa23274c9
[  112.664714] R13: ffff9feebb5e4070 R14: 0000000000000000 R15: 0000000000000000
[  112.664715] FS:  00007f9b250f1740(0000) GS:ffff9feebda00000(0000) knlGS:0000000000000000
[  112.664716] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  112.664717] CR2: 00007f1632bff810 CR3: 000000007b6b2004 CR4: 00000000000606f0
[  112.664722] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  112.664723] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  112.664724] Call Trace:
[  112.664734]  sysfs_create_files+0x73/0x90
[  112.664737]  __device_add_disk+0x292/0x4b0
[  112.664740]  loop_add+0x1e4/0x250 [loop]
[  112.664743]  loop_control_ioctl+0xa7/0x140 [loop]
[  112.664745]  do_vfs_ioctl+0x43d/0x6c0
[  112.664748]  ? syscall_trace_enter+0x19c/0x2e0
[  112.664750]  ksys_ioctl+0x5e/0x90
[  112.664752]  __x64_sys_ioctl+0x16/0x20
[  112.664754]  do_syscall_64+0x4e/0x140
[  112.664756]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[  112.664758] RIP: 0033:0x7f9b251ea25b
[  112.664759] Code: 0f 1e fa 48 8b 05 25 9c 0c 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d f5 9b 0c 00 f7 d8 64 89 01 48
[  112.664760] RSP: 002b:00007ffd08568338 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
[  112.664765] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f9b251ea25b
[  112.664766] RDX: 0000000000100000 RSI: 0000000000004c80 RDI: 0000000000000003
[  112.664767] RBP: 00007ffd08568400 R08: 000000000000000a R09: 0000000000000012
[  112.664768] R10: 00007ffd08565b31 R11: 0000000000000246 R12: 0000000000000003
[  112.664770] R13: 00007ffd08568344 R14: 000055a4a27d4020 R15: 00007ffd08568400
[  112.664772] ---[ end trace 1f3c07c7bf2ac59c ]---
[  112.664781] loop1048576: failed to create sysfs files for events
[  112.664791] kobject_add_internal failed for integrity (error: -2 parent: loop1048576)

Subsequent detachement failure:

[root@KVM-NEU ~]# losetup -D
448: loopdev:      CXT: [0x7ffd589521c0]: initialize context
448: loopdev:      CXT: [0x7ffd589521c0]: init: ignore ioctls
448: loopdev:      CXT: [0x7ffd589521c0]: init: loop-control detected 
448: loopdev:     ITER: [0x7ffd58952350]: initialize
448: loopdev:     ITER: [0x7ffd58952350]: next
448: loopdev:     ITER: [0x7ffd58952350]: scanning /sys/block
448: loopdev:     ITER: [0x7ffd58952350]: check .
448: loopdev:     ITER: [0x7ffd58952350]: check ..
448: loopdev:     ITER: [0x7ffd58952350]: check loop1
448: loopdev:     ITER: [0x7ffd58952350]: check loop6
448: loopdev:     ITER: [0x7ffd58952350]: check loop4
448: loopdev:     ITER: [0x7ffd58952350]: check sr0
448: loopdev:     ITER: [0x7ffd58952350]: check loop2
448: loopdev:     ITER: [0x7ffd58952350]: check loop0
448: loopdev:      CXT: [0x7ffd589521c0]: loop0 name assigned
448: loopdev:     ITER: [0x7ffd58952350]: /dev/loop0 exist
448: loopdev:      CXT: [0x7ffd589521c0]: get_offset [rc=0]
448: loopdev:      CXT: [0x7ffd589521c0]: open /dev/loop0 [ro]: No such file or directory
448: loopdev:      CXT: [0x7ffd589521c0]: LOOP_CLR_FD failed: No such device or address
losetup: /dev/loop0: detach failed: No such device or address
448: loopdev:     ITER: [0x7ffd58952350]: next
448: loopdev:     ITER: [0x7ffd58952350]: scanning /sys/block
448: loopdev:     ITER: [0x7ffd58952350]: check dm-0
448: loopdev:     ITER: [0x7ffd58952350]: check loop7
448: loopdev:     ITER: [0x7ffd58952350]: check sda
448: loopdev:     ITER: [0x7ffd58952350]: check loop5
448: loopdev:     ITER: [0x7ffd58952350]: check loop3
448: loopdev:     ITER: [0x7ffd58952350]: de-initialize
448: loopdev:     ITER: [0x7ffd58952350]: de-initialize
448: loopdev:      CXT: [0x7ffd589521c0]: de-initialize
448: loopdev:      CXT: [0x7ffd589521c0]: closing old open fd
448: loopdev:     ITER: [0x7ffd58952350]: de-initialize
[root@KVM-NEU ~]# losetup
450: loopdev:      CXT: [0x7ffe522d9860]: initialize context
450: loopdev:      CXT: [0x7ffe522d9860]: init: ignore ioctls
450: loopdev:      CXT: [0x7ffe522d9860]: init: loop-control detected 
450: loopdev:     ITER: [0x7ffe522d99f0]: initialize
450: loopdev:     ITER: [0x7ffe522d99f0]: next
450: loopdev:     ITER: [0x7ffe522d99f0]: scanning /sys/block
450: loopdev:     ITER: [0x7ffe522d99f0]: check .
450: loopdev:     ITER: [0x7ffe522d99f0]: check ..
450: loopdev:     ITER: [0x7ffe522d99f0]: check loop1
450: loopdev:     ITER: [0x7ffe522d99f0]: check loop6
450: loopdev:     ITER: [0x7ffe522d99f0]: check loop4
450: loopdev:     ITER: [0x7ffe522d99f0]: check sr0
450: loopdev:     ITER: [0x7ffe522d99f0]: check loop2
450: loopdev:     ITER: [0x7ffe522d99f0]: check loop0
450: loopdev:      CXT: [0x7ffe522d9860]: loop0 name assigned
450: loopdev:     ITER: [0x7ffe522d99f0]: /dev/loop0 exist
450: loopdev:      CXT: [0x7ffe522d9860]: get_offset [rc=0]
450: loopdev:      CXT: [0x7ffe522d9860]: get_sizelimit [rc=0]
450: loopdev:      CXT: [0x7ffe522d9860]: get_offset [rc=0]
450: loopdev:      CXT: [0x7ffe522d9860]: get_backing_file [/root/somefile]
450: loopdev:      CXT: [0x7ffe522d9860]: get_blocksize [rc=0]
450: loopdev:     ITER: [0x7ffe522d99f0]: next
450: loopdev:     ITER: [0x7ffe522d99f0]: scanning /sys/block
450: loopdev:     ITER: [0x7ffe522d99f0]: check dm-0
450: loopdev:     ITER: [0x7ffe522d99f0]: check loop7
450: loopdev:     ITER: [0x7ffe522d99f0]: check sda
450: loopdev:     ITER: [0x7ffe522d99f0]: check loop5
450: loopdev:     ITER: [0x7ffe522d99f0]: check loop3
450: loopdev:     ITER: [0x7ffe522d99f0]: de-initialize
450: loopdev:     ITER: [0x7ffe522d99f0]: de-initialize
NAME       SIZELIMIT OFFSET AUTOCLEAR RO BACK-FILE      DIO LOG-SEC
/dev/loop0         0      0         0  0 /root/somefile   0     512
450: loopdev:      CXT: [0x7ffe522d9860]: de-initialize
450: loopdev:     ITER: [0x7ffe522d99f0]: de-initialize

@karelzak
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karelzak commented Dec 4, 2019 via email

@mator
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mator commented Jun 8, 2020

https://www.spinics.net/lists/linux-block/msg54898.html

@KumanekoSakura
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A patch to reject /dev/loopX with X >= 1048576 has arrived to upstream kernel as
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e338924bd05d6e71574bc13e310c89e10e49a8a5 .

Please backport to your distribution's kernel as needed.

@karelzak
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Thanks!

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