qcow2: Fix L1 allocation size in qcow2_snapshot_load_tmp() (CVE-2014-0145)

qcow2: Fix L1 allocation size in qcow2_snapshot_load_tmp() (CVE-2014-0145)

For the L1 table to loaded for an internal snapshot, the code allocated
only enough memory to hold the currently active L1 table. If the
snapshot's L1 table is actually larger than the current one, this leads
to a buffer overflow.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
(cherry picked from commit c05e4667be91b46ab42b5a11babf8e84d476cc6b)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>