Sandbox: Mount a temporary directory on /dev/shm - #1484
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It's a good temporary measure before we rewrite the sandbox code.
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Isolate's default mount rules don't have
norecfor/dev, The host OS has a separate (tmpfs) mount point for/dev/shmwhich is rw and world-writable, so isolate inherits it as rw. This means any solution can write to /dev/shm and communicate with another sandbox. Fix by mounting a fresh tmpfs on /dev/shm.I didn't find this myself, I saw some CMS fork where a commit message mentioned dev/shm, and made a note to investigate it later, and well, turns out it is indeed problematic...
Maybe a better fix is to change the default rules in isolate, to add norec to the /dev rule.