[Bug 1673957] Re: virtfs: mapped-xattr on mount point

[Christian Schoenebeck]

Independent of the planned tracker transition: this issue would require
more information by original reporter anyway.

>From the information provided so far, I cannot reproduce this problem,
and the error messages don't look like common misconfigurations on host
side like wrong permissions, AppArmor policies or something like that.
Especially the error message "Cannnot allocate memory" looks weird to
me. So I think there should at least be more details about the host
system this was deployed on.

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https://bugs.launchpad.net/bugs/1673957

Title:
  virtfs: mapped-xattr on mount point

Status in QEMU:
  Incomplete

Bug description:
  With
    -virtfs local,path="/tmp",security_model=mapped-xattr,mount_tag="shared2"
  in the qemu command line,
    shared2 on /mnt/testbis type 9p 
(rw,sync,dirsync,relatime,trans=virtio,version=9p2000.L,msize=262144)
  in the guest mount points, and
    tmpfs on /tmp type tmpfs (rw,nosuid,nodev)
  in the host mount points (with CONFIG_TMPFS_XATTR=y according to zgrep 
/proc/config.gz), running qemu as user "vm-test", trying to "touch a" in 
/mnt/testbis on the VM fails with "Operation not supported". In addition, no 
file or directory actually present in the host's /tmp can be seen in the 
guest's /mnt/testbis.

  When trying to replace "/tmp" with "/tmp/aaa" on the host, with
  /tmp/aaa owned by root:root, still running qemu as vm-test, trying to
  run "ls" in the guest's /mnt/testbis fails with the weird "ls: reading
  directory '.': Cannot allocate memory", while the directory is empty.

  After a "chown vm-test /tmp/aaa", the guest can list the files
  (despite the permissions already allowing it to do so before), but
  still not write new files: "cannot touch 'b': Operation not
  supported".

  Do you have a pointer as to what is happening?

  PS: complete setup is running all this inside a qemu VM that I use for
  testing, I guess it shouldn't matter but saying it just in case

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