[Qemu-devel] 9pfs: unreadable dirs with random errors in guest

[Michael Tokarev]

When I mount a 9pfs filesystem in guest with no write permission for
some dirs, I'm getting strange errors in guest.

Host (as a regular user):
 qemu-system-x86_64 -virtfs 
local,path=/,security_model=mapped-file,mount_tag=tag

Guest:
 # mount -t 9p -o trans=virtio,ro tag /mnt
 # ls /mnt
 ls: reading directory /mnt: Unknown error 593
 # ls /mnt/dev
 ls: reading directory /mnt/dev: Unknown error 849
 # ls /mnt/tmp
 [works]
 # ls /mnt/root
 ls: cannot open directory /mnt/root: Permission denied

So, it reports errors while trying to _read_ (not open)
readable but non-writable dirs, and these errors are _random_.
It correctly reports errors when trying to open an unreadable
dir.

This is 1.4.0.  Similar problem exists with earlier versions
of qemu.

Thanks!

/mjt