tcmur: fail cross-device XCOPY requests
tcmur: fail cross-device XCOPY requests

tcmu-runner can't determine whether the device(s) referred to in XCOPY
Copy Source/Copy Destination (CSCD) descriptors should be accessible to
the initiator via transport settings, ACLs, etc. Consequently, fail
XCOPY requests with CSCD descriptors which refer to any device other
than where the XCOPY request is processed.

References: CVE-2020-28374
Fixes: 9c86bd0 ("tcmur: Add emulate XCOPY command support")
Signed-off-by: David Disseldorp <589a549dc9f982d9f46aeeb82a09ab6d87ccf1d8@suse.de>
Reviewed-by: Lee Duncan <c26a906ef95597994b980de8dd0b0650fa5f3921@suse.com>

open-iscsi/tcmu-runner,open-iscsi/tcmu-runner