On [*] Daniel Berrangé commented:
The QEMU guest agent protocol is not sensible way to access huge
files inside the guest. It requires the inefficient process of
reading the entire data into memory than duplicating it again in
base64 format, and then copying it again in the JSON serializer /
monitor code.
For arbitrary general purpose file access, especially for large
files, use a real file transfer program or use a network block
device, not the QEMU guest agent.
To avoid bug reports as BZ#1594054 (CVE-2018-12617), follow his
suggestion to put a low, hard limit on "count" in the guest agent
QAPI schema, and don't allow count to be larger than 48 MB.
[*] https://www.mail-archive.com/qemu-devel@nongnu.org/msg693176.html
Fixes: CVE-2018-12617
Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1594054
Reported-by: Fakhri Zulkifli <mohdfakhrizulkifli@gmail.com>
Suggested-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
*update schema documentation to indicate 48MB limit instead of 10MB
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
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