A flaw was found in the Udisks daemon, where it allows unprivileged
users to create loop devices using the D-BUS system. This is
achieved via the loop device handler, which handles requests sent
through the D-BUS interface. As two of the parameters of this
handle, it receives the file descriptor list and index specifying
the file where the loop device should be backed. The function
itself validates the index value to ensure it isn't bigger
than the maximum value allowed. However, it fails to validate the
lower bound, allowing the index parameter to be a negative value.
Under these circumstances, an attacker can cause the UDisks daemon
to crash or perform a local privilege escalation by gaining access
to files owned by privileged users.