Re: [PULL for-5.0 4/4] qga: Restrict guest-file-read count to 48 MB to avoid crashes

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 4/15/20 5:22 PM, Michael Roth wrote:
> From: Philippe Mathieu-Daudé <philmd@redhat.com>
> 
> 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

Thanks!

> Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
> ---
>   qga/commands.c       | 9 ++++++++-
>   qga/qapi-schema.json | 6 ++++--
>   2 files changed, 12 insertions(+), 3 deletions(-)