libxc: [CVE-2011-1583] pv kernel image validation

libxc: [CVE-2011-1583] pv kernel image validation

The functions which interpret the kernel image supplied for a
paravirtualised guest, and decompress it into memory when booting the
domain, are incautious.  Specifically:

 (i) Integer overflow in the decompression loop memory allocator might
    result in overrunning the buffer used for the decompressed image;
 (ii) Integer overflows and lack of checking of certain length fields
    can result in the loader reading its own address space beyond the
    size of the supplied kernel image file.
 (iii) Lack of error checking in the decompression loop can lead to an
    infinite loop.

This patch fixes these problems.

CVE-2011-1583.

Signed-off-by: Ian Campbell <Ian.Campbell@eu.citrix.com>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>