[Bug 1889033] [NEW] qemu-img permission denied on vmdk creation on CIFS share

[Hgkamath]

Public bug reported:


- on a CIFS mount qemu-img claims not to have permissions to write into a file.
- VMDK sparse file creation succeeds
- VMDK Flat file creation create the flat-file, but fails to write the 
description-file
- VMDK flat file creation succeeds on native linux mount such as ~/tmp or /tmp
- same effect as root or non-root
- same effect with selinux setenforce 0

a) I would have expected that the monolithic flat would have created only one 
large file just like sparse, but it seems to create a description file, in 
addition to the storing file.
b) I am aware that qemu-img may have problem opening very large files on CIFS, 
however, this file is not very large

Windows-10 latest updated 2004 19041.388
Linux VM, Fedora-32 in Virtualbox 6.1.12 
# rpm -qa | grep  qemu-img
qemu-img-4.2.0-7.fc32.x86_64

mount options: 
mount -t cifs //10.x,x,x/$shname  /mnt/hshare -o 
defaults,username=gana,rw,uid=1000,gid=1000,vers=3.0

[root@fedora ~]# cd /mnt/hshare/some/folder/createvmdk/
[root@fedora createvmdk]# qemu-img create -f vmdk test1.vmdk 100M -o 
subformat=monolithicFlat
Formatting 'test1.vmdk', fmt=vmdk size=104857600 compat6=off 
hwversion=undefined subformat=monolithicFlat
qemu-img: test1.vmdk: Could not write description: Permission denied
[root@fedora createvmdk]# ls -l test1*.*
-rwxr-xr-x. 1 gana gana 104857600 Jul 26 23:02 test1-flat.vmdk
-rwxr-xr-x. 1 gana gana         0 Jul 26 23:02 test1.vmdk
[root@fedora createvmdk]# du -k test1*.*
0       test1-flat.vmdk
0       test1.vmdk
# (doesn't seem to be really flat)

creation in /tmp works
# cd /tmp
[root@fedora tmp]# qemu-img create -f vmdk test1.vmdk 100M -o 
subformat=monolithicFlat
Formatting 'test1.vmdk', fmt=vmdk size=104857600 compat6=off 
hwversion=undefined subformat=monolithicFlat
[root@fedora tmp]# ls -l /tmp/test1*.*
-rw-r--r--. 1 root root 104857600 Jul 26 22:43 /tmp/test1-flat.vmdk
-rw-r--r--. 1 root root       313 Jul 26 22:43 /tmp/test1.vmdk
[root@fedora createvmdk]# du -k /tmp/test1*.*
4       /tmp/test1-flat.vmdk
4       /tmp/test1.vmdk

[root@fedora createvmdk]# cat /tmp/test1.vmdk
# Disk DescriptorFile
version=1
CID=5f13c13d
parentCID=ffffffff
createType="monolithicFlat"

# Extent description
RW 204800 FLAT "test1-flat.vmdk" 0

# The Disk Data Base
#DDB

ddb.virtualHWVersion = "4"
ddb.geometry.cylinders = "203"
ddb.geometry.heads = "16"
ddb.geometry.sectors = "63"
ddb.adapterType = "ide"


On the other-hand creating a sparse file works
cd /mnt/hshare/some/folder/createvmdk/
[root@fedora createvmdk]# qemu-img create -f vmdk test2.vmdk 100M -o 
subformat=monolithicSparse
Formatting 'test2.vmdk', fmt=vmdk size=104857600 compat6=off 
hwversion=undefined subformat=monolithicSparse
[root@fedora createvmdk]# ls l test2*.*
-rwxr-xr-x. 1 gana gana     65536 Jul 26 22:52 test2.vmdk
[root@fedora createvmdk]#  du -k  /tmp/test2*.*
12      /tmp/test2.vmdk

test2.vmdk is a binary file
inside it, located among garbled ascii characters is an embedded VMDK 
description
````
# Disk DescriptorFile
version=1
CID=cf302a20
parentCID=ffffffff
createType="monolithicSparse"

# Extent description
RW 204800 SPARSE "test2.vmdk"

# The Disk Data Base
#DDB

ddb.virtualHWVersion = "4"
ddb.geometry.cylinders = "203"
ddb.geometry.heads = "16"
ddb.geometry.sectors = "63"
ddb.adapterType = "ide"
```

** Affects: qemu
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1889033

Title:
  qemu-img permission denied on vmdk creation on CIFS share

Status in QEMU:
  New

Bug description:
  
  - on a CIFS mount qemu-img claims not to have permissions to write into a 
file.
  - VMDK sparse file creation succeeds
  - VMDK Flat file creation create the flat-file, but fails to write the 
description-file
  - VMDK flat file creation succeeds on native linux mount such as ~/tmp or /tmp
  - same effect as root or non-root
  - same effect with selinux setenforce 0

  a) I would have expected that the monolithic flat would have created only one 
large file just like sparse, but it seems to create a description file, in 
addition to the storing file.
  b) I am aware that qemu-img may have problem opening very large files on 
CIFS, however, this file is not very large

  Windows-10 latest updated 2004 19041.388
  Linux VM, Fedora-32 in Virtualbox 6.1.12 
  # rpm -qa | grep  qemu-img
  qemu-img-4.2.0-7.fc32.x86_64

  mount options: 
  mount -t cifs //10.x,x,x/$shname  /mnt/hshare -o 
defaults,username=gana,rw,uid=1000,gid=1000,vers=3.0

  [root@fedora ~]# cd /mnt/hshare/some/folder/createvmdk/
  [root@fedora createvmdk]# qemu-img create -f vmdk test1.vmdk 100M -o 
subformat=monolithicFlat
  Formatting 'test1.vmdk', fmt=vmdk size=104857600 compat6=off 
hwversion=undefined subformat=monolithicFlat
  qemu-img: test1.vmdk: Could not write description: Permission denied
  [root@fedora createvmdk]# ls -l test1*.*
  -rwxr-xr-x. 1 gana gana 104857600 Jul 26 23:02 test1-flat.vmdk
  -rwxr-xr-x. 1 gana gana         0 Jul 26 23:02 test1.vmdk
  [root@fedora createvmdk]# du -k test1*.*
  0       test1-flat.vmdk
  0       test1.vmdk
  # (doesn't seem to be really flat)

  creation in /tmp works
  # cd /tmp
  [root@fedora tmp]# qemu-img create -f vmdk test1.vmdk 100M -o 
subformat=monolithicFlat
  Formatting 'test1.vmdk', fmt=vmdk size=104857600 compat6=off 
hwversion=undefined subformat=monolithicFlat
  [root@fedora tmp]# ls -l /tmp/test1*.*
  -rw-r--r--. 1 root root 104857600 Jul 26 22:43 /tmp/test1-flat.vmdk
  -rw-r--r--. 1 root root       313 Jul 26 22:43 /tmp/test1.vmdk
  [root@fedora createvmdk]# du -k /tmp/test1*.*
  4       /tmp/test1-flat.vmdk
  4       /tmp/test1.vmdk

  [root@fedora createvmdk]# cat /tmp/test1.vmdk
  # Disk DescriptorFile
  version=1
  CID=5f13c13d
  parentCID=ffffffff
  createType="monolithicFlat"

  # Extent description
  RW 204800 FLAT "test1-flat.vmdk" 0

  # The Disk Data Base
  #DDB

  ddb.virtualHWVersion = "4"
  ddb.geometry.cylinders = "203"
  ddb.geometry.heads = "16"
  ddb.geometry.sectors = "63"
  ddb.adapterType = "ide"

  
  On the other-hand creating a sparse file works
  cd /mnt/hshare/some/folder/createvmdk/
  [root@fedora createvmdk]# qemu-img create -f vmdk test2.vmdk 100M -o 
subformat=monolithicSparse
  Formatting 'test2.vmdk', fmt=vmdk size=104857600 compat6=off 
hwversion=undefined subformat=monolithicSparse
  [root@fedora createvmdk]# ls l test2*.*
  -rwxr-xr-x. 1 gana gana     65536 Jul 26 22:52 test2.vmdk
  [root@fedora createvmdk]#  du -k  /tmp/test2*.*
  12      /tmp/test2.vmdk

  test2.vmdk is a binary file
  inside it, located among garbled ascii characters is an embedded VMDK 
description
  ````
  # Disk DescriptorFile
  version=1
  CID=cf302a20
  parentCID=ffffffff
  createType="monolithicSparse"

  # Extent description
  RW 204800 SPARSE "test2.vmdk"

  # The Disk Data Base
  #DDB

  ddb.virtualHWVersion = "4"
  ddb.geometry.cylinders = "203"
  ddb.geometry.heads = "16"
  ddb.geometry.sectors = "63"
  ddb.adapterType = "ide"
  ```

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