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@prandla prandla commented Jul 28, 2025

Isolate's default mount rules don't have norec for /dev, The host OS has a separate (tmpfs) mount point for /dev/shm which 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.

@prandla prandla requested a review from gollux August 22, 2025 01:15
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It's a good temporary measure before we rewrite the sandbox code.

@prandla prandla merged commit f942b02 into cms-dev:main Aug 22, 2025
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@prandla prandla deleted the bugfix-dev-shm branch August 22, 2025 12:34
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