I'm amazed that polyinstantiation of directories via pam_namespace.so[1] is so unheard of. Setting this up fixes almost all of the qualms mentioned in the article by giving each user their own mount namespace with an isolated /tmp directory (and others if configured). Still though, this wouldn't prevent poorly written applications using /tmp from clashing with others that are running under the same user.
It's relatively easy to set up[2] and provides a pretty huge defense mitigation against abusing /tmp.
[1] https://www.man7.org/linux/man-pages/man8/pam_namespace.8.ht...
[2] https://docs.redhat.com/en/documentation/red_hat_enterprise_...
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