Fix auto-uid-allocation in Docker containers #7692
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thufschmitt
previously requested changes
Jan 30, 2023
This didn't work because sandboxing doesn't work in Docker. However, the sandboxing check is done lazily - after clone(CLONE_NEWNS) fails, we retry with sandboxing disabled. But at that point, we've already done UID allocation under the assumption that user namespaces are enabled. So let's get rid of the "goto fallback" logic and just detect early whether user / mount namespaces are enabled. This commit also gets rid of a compatibility hack for some ancient Linux kernels (<2.13).
In unprivileged podman containers, /proc is not fully visible (there are other filesystems mounted on subdirectories of /proc). Therefore we can't mount a new /proc in the sandbox that matches the PID namespace of the sandbox. So this commit automatically disables sandboxing if /proc is not fully visible.
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Motivation
Fixes
This didn't work because sandboxing doesn't work in Docker. However, the sandboxing check is done lazily - after
clone(CLONE_NEWNS)fails, we retry with sandboxing disabled. But at that point, we've already done UID allocation under the assumption that user namespaces are enabled.So let's get rid of the "goto fallback" logic and just detect early whether user / mount namespaces are enabled.
This commit also gets rid of a compatibility hack for some ancient Linux kernels (<2.13).
It also adds a check to automatically disable sandboxing in unprivileged podman containers, since that doesn't work.
Checklist for maintainers
Maintainers: tick if completed or explain if not relevant
tests/**.shsrc/*/tests