Comment 7 for bug 1643609

Reviewed: https://review.fuel-infra.org/29313
Submitter: Pkgs Jenkins <email address hidden>
Branch: 9.0/mitaka

Commit: ed209ae75f0aa9ab964ed0f3421f9f89a9f09ae9
Author: Sean Dague <email address hidden>
Date: Mon Dec 12 15:36:10 2016

Bump prlimit cpu time for qemu from 2 to 8

We've got user reported bugs that when opperating with slow NFS
backends with large (30+ GB) disk files, the prlimit of cpu_time 2 is
guessed to be the issue at hand because if folks hot patch a qemu-img
that runs before the prlimitted one, the prlimitted one succeeds.

This increases the allowed cpu timeout, as well as tweaking the error
message so that we return something more prescriptive when the
qemu-img command fails with prlimit abort.

The original bug (#1449062) the main mitigation concern here was a
carefully crafted image that gets qemu-img to generate > 1G of json,
and hence could be a node attack vector. cpu_time was never mentioned,
and I think was added originally as a belt and suspenders addition. As
such, bumping it to 8 seconds shouldn't impact our protection in any
real way.

Change-Id: I1f4549b787fd3b458e2c48a90bf80025987f08c4
Closes-Bug: #1643609
(cherry picked from commit b78b1f8ce3aa407307a6adc5c60de1e960547897)