[delamon]

The attack gives you ability to overwrite any cached page. So you don't need to be root to "edit" /etc/passwd.

[quantummagic]

Not of the host system, assuming we're talking about a compromised VM, running as a non-root user.

[delamon]

I assume you mean container, not VM. But yes, container makes it harder.

[minimaltom]

Worth adding also that you can only use these vectors to corrupt the page cache for files reachable in your mount namespace.

Usually with containers, almost nothing is shared with the host namespaces (tho likely shared with other container namespaces, hopefully none of those are --priv).