x86/mm: Prevent leaking domain mappings in paging_log_dirty_op()

x86/mm: Prevent leaking domain mappings in paging_log_dirty_op()

Coverity ID: 1135374 1135375 1135376 1135377

If {copy_to,clear}_guest_offset() fails, we would leak the domain mappings for
l4 thru l1.

Fixing this requires having conditional unmaps on the faulting path, which in
turn requires explicitly initialising the pointers to NULL because of the
early ENOMEM exit.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <JBeulich@suse.com>
Acked-by: Tim Deegan <tim@xen.org>
master commit: 0725f326358cbb2ba7f9626976e346b963d74c37
master date: 2013-12-17 16:38:07 +0100