qvm-block allows attaching the same device twice

[marmarek]

Reported by marmarek on 9 Feb 2015 13:18 UTC
Steps to reproduce:

1. add external hdd to daily appvm

~]$ qvm-block -a daily dom0:sde1

1. list the device

...
dom0:sde1 (data) 488 GiB (attached to 'daily' as 'xvdi')

1. mount at daily appvm

user ~]$ sudo mount /dev/xvdi /mnt

1. accidentaly add to daily vm again on dom0

~]$ qvm-block -a daily dom0:sde1
~]$ qvm-block
...
dom0:sde1 (data) 488 GiB (attached to 'daily' as 'xvdj')
...

there is double add to daily (appVM) with double device mount point, but on daily (appVM) still mounted as /dev/xvdi , and we can mount again as /dev/xvdj

when delete on dom0

~]$ qvm-block -d dom0:sde1
~]$ qvm-block
...
dom0:sde1 (data) 488 GiB

but, on daily (appVM) still can access the mount point (rw mode) on /dev/xvdi when do umount at daily (appVM) , umount successful but on dom0 was not attached to any appVM

https://groups.google.com/d/msgid/qubes-users/2dd14e12-4a31-4b33-b505-48aaa48f1a02%40googlegroups.com

Migrated-From: https://wiki.qubes-os.org/ticket/950

[marmarek]

This may appear as the device is still there, because it is mounted, but in
fact any access to the device will fail. The only data still available is that
being cached by the kernel.