If a system admin provides a disk (which supports the discard aka TRIM or SCSI UNMAP) to a guest as read-only - there are no checks done.
A privileged guest user could use this flaw to destroy data on the disk to which he otherwise wouldn't have write access to.
This issue did not affect the versions of the kernel-xen package as shipped with Red Hat Enterprise Linux 5 as it has no support for BLKIF_OP_DISCARD.
This issue did not affect Red Hat Enterprise Linux 6 and Red Hat Enterprise MRG 2.
Created kernel tracking bugs for this issue
Affects: fedora-all [bug 971148]
For future reference: