* src/qemu/qemu_driver.c (qemudDomainRestore): A corrupt save file
(in particular, a too-large header.xml_len value) would cause an
unwarranted out-of-memory error.  Do not trust the just-read
header.xml_len.  Instead, merely use that as a hint, and
read/allocate up to that number of bytes from the file.
Also verify that header.xml_len is positive; if it were negative,
passing it to virFileReadLimFD could cause trouble.