[dm-devel] dm crypt: export sysfs of kcryptd workqueue - broken dmsetup reload

Thu Dec 24 02:16:22 UTC 2020

Sorry for the bug.

It seems that the reload table routine will create new table prior to
destroying old table, in which case the duplicate sysfs name collision
happens when creating the new table.

Maybe we could add a hash string (hashed from the address of struct
dm_table) as part of the sysfs name such as kcryptd-252:0-dsfggfh...,
since the value of 'struct dm_table *' differs at that time. But I
wonder it may not be acceptable to export such nonsense hash string to
the user space....

On 12/24/20 5:48 AM, Ignat Korchagin wrote:
> Hi,
> 
> Looks like a2b8b2d975673b1a50ab0bcce5d146b9335edfad broke the ability
> to reload dm-crypt targets.
> 
> I usually used to enable additional flags like this on an existing
> dm-crypt instance:
> 
> ignat at dev:~$ sudo dmsetup table --showkeys test | sed 's/$/ 2
> no_read_workqueue no_write_workqueue/' | sudo dmsetup reload test
> 
> Now the command fails with below:
> 
> device-mapper: reload ioctl on test  failed: Cannot allocate memory
> Command failed.
> 
> I also get this in the kernel log:
> 
> [   61.138067][ T2594] sysfs: cannot create duplicate filename
> '/devices/virtual/workqueue/kcryptd-251:0'
> [   61.139949][ T2594] CPU: 0 PID: 2594 Comm: dmsetup Not tainted 5.10.0+ #48
> [   61.141176][ T2594] Hardware name: QEMU Standard PC (i440FX + PIIX,
> 1996), BIOS 0.0.0 02/06/2015
> [   61.142726][ T2594] Call Trace:
> [   61.143293][ T2594]  dump_stack+0x7d/0xa3
> [   61.144030][ T2594]  sysfs_warn_dup.cold+0x17/0x24
> [   61.144897][ T2594]  sysfs_create_dir_ns+0x1f3/0x270
> [   61.145844][ T2594]  ? sysfs_create_mount_point+0x90/0x90
> [   61.146830][ T2594]  ? _raw_spin_lock+0x81/0xd0
> [   61.147674][ T2594]  kobject_add_internal+0x2a6/0x860
> [   61.148594][ T2594]  ? table_load+0x2d7/0x690
> [   61.149372][ T2594]  ? ctl_ioctl+0x3a1/0x950
> [   61.150122][ T2594]  kobject_add+0x125/0x190
> [   61.150914][ T2594]  ? kset_create_and_add+0x160/0x160
> [   61.151812][ T2594]  ? unpoison_range+0x3a/0x60
> [   61.152616][ T2594]  ? ____kasan_kmalloc.constprop.0+0x82/0xa0
> [   61.153633][ T2594]  ? unpoison_range+0x3a/0x60
> [   61.154459][ T2594]  device_add+0x2d7/0x1a40
> [   61.155235][ T2594]  ? dev_set_name+0xb0/0xe0
> [   61.156001][ T2594]  ? memset+0x20/0x40
> [   61.156680][ T2594]  ? __fw_devlink_link_to_suppliers+0x560/0x560
> [   61.157762][ T2594]  ? pm_runtime_init+0x2a3/0x380
> [   61.158646][ T2594]  workqueue_sysfs_register+0x17e/0x370
> [   61.159593][ T2594]  alloc_workqueue+0x559/0xb50
> [   61.160401][ T2594]  ? workqueue_sysfs_register+0x370/0x370
> [   61.161387][ T2594]  ? sscanf+0xab/0xe0
> [   61.162063][ T2594]  ? bioset_init+0x41a/0x710
> [   61.162870][ T2594]  crypt_ctr+0x24d5/0x2f90
> [   61.163624][ T2594]  ? crypt_ctr_cipher_new.constprop.0+0xa30/0xa30
> [   61.164703][ T2594]  ? realloc_argv+0xd2/0x110
> [   61.165492][ T2594]  ? dm_table_destroy+0x410/0x410
> [   61.166357][ T2594]  dm_table_add_target+0x45d/0xc40
> [   61.167239][ T2594]  ? dm_table_create+0xd8/0x320
> [   61.168090][ T2594]  ? dm_split_args+0x580/0x580
> [   61.168910][ T2594]  ? __mutex_lock_slowpath+0x10/0x10
> [   61.169800][ T2594]  ? dm_table_create+0x12b/0x320
> [   61.170651][ T2594]  table_load+0x2d7/0x690
> [   61.171395][ T2594]  ? __kasan_kmalloc_large+0x89/0xb0
> [   61.172295][ T2594]  ? dev_suspend+0x4a0/0x4a0
> [   61.173109][ T2594]  ? __kmalloc_node+0x275/0x320
> [   61.173960][ T2594]  ? __might_fault+0x4f/0x70
> [   61.174733][ T2594]  ctl_ioctl+0x3a1/0x950
> [   61.175492][ T2594]  ? dev_suspend+0x4a0/0x4a0
> [   61.176248][ T2594]  ? free_params+0x30/0x30
> [   61.176968][ T2594]  dm_ctl_ioctl+0xa/0x10
> [   61.177659][ T2594]  __x64_sys_ioctl+0x7ff/0x1110
> [   61.178472][ T2594]  ? generic_block_fiemap+0x60/0x60
> [   61.179308][ T2594]  do_syscall_64+0x33/0x40
> [   61.180045][ T2594]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> [   61.181007][ T2594] RIP: 0033:0x7f48230e0427
> [   61.181722][ T2594] Code: 00 00 90 48 8b 05 69 aa 0c 00 64 c7 00 26
> 00 00 00 48 c7 c0 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 b8 10
> 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 39 aa 0c 00 f7 d8
> 64 89 01 48
> [   61.184908][ T2594] RSP: 002b:00007ffd1469cb68 EFLAGS: 00000202
> ORIG_RAX: 0000000000000010
> [   61.186262][ T2594] RAX: ffffffffffffffda RBX: 00007f48231bea7f
> RCX: 00007f48230e0427
> [   61.187590][ T2594] RDX: 0000556251e1dea0 RSI: 00000000c138fd09
> RDI: 0000000000000003
> [   61.188970][ T2594] RBP: 00007ffd1469cc20 R08: 00007f482320d310
> R09: 00007ffd1469c9d0
> [   61.190290][ T2594] R10: 00007f482320c65a R11: 0000000000000202
> R12: 00007f482320c65a
> [   61.191639][ T2594] R13: 00007f482320c65a R14: 00007f482320c65a
> R15: 00007f482320c65a
> [   61.193014][ T2594] kobject_add_internal failed for kcryptd-251:0
> with -EEXIST, don't try to register things with the same name in the
> same directory.
> [   61.201542][ T2594] device-mapper: table: 251:0: crypt: Couldn't
> create kcryptd queue
> [   61.203050][ T2594] device-mapper: ioctl: error adding target to table
> 
> Seems we're missing a clean-up somewhere, so it tries to create multiple queues.
> 
> Regards,
> Ignat
> 
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> 

-- 
Thanks,
Jeffle