runsc: support unprivileged user namespace mappings using SysProcAttr#12812
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runsc: support unprivileged user namespace mappings using SysProcAttr#12812copybara-service[bot] wants to merge 1 commit intomasterfrom
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When running in rootless mode, runsc currently relies on newuidmap and newgidmap to set up user namespace mappings. However, these binaries are setuid and might be unavailable or disabled in certain environments, such as nested unprivileged containers. If the requested mappings are simple (exactly one mapping of size 1 that maps to the current effective UID/GID), the Linux kernel allows an unprivileged process to set its own mappings. Go's os/exec package supports this via SysProcAttr.UidMappings and SysProcAttr.GidMappings. This change adds a CanUseUnprivilegedMapping helper to check if the requested mappings are compatible with this unprivileged approach. If they are, createSandboxProcess and createGoferProcess will configure cmd.SysProcAttr directly, bypassing the need for newuidmap/newgidmap. For more complex mappings, runsc continues to fall back to the existing newuidmap/newgidmap mechanism. PiperOrigin-RevId: 891146229
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runsc: support unprivileged user namespace mappings using SysProcAttr
When running in rootless mode, runsc currently relies on newuidmap and
newgidmap to set up user namespace mappings. However, these binaries are
setuid and might be unavailable or disabled in certain environments, such
as nested unprivileged containers.
If the requested mappings are simple (exactly one mapping of size 1 that
maps to the current effective UID/GID), the Linux kernel allows an
unprivileged process to set its own mappings. Go's os/exec package
supports this via SysProcAttr.UidMappings and SysProcAttr.GidMappings.
This change adds a CanUseUnprivilegedMapping helper to check if the
requested mappings are compatible with this unprivileged approach. If
they are, createSandboxProcess and createGoferProcess will configure
cmd.SysProcAttr directly, bypassing the need for newuidmap/newgidmap.
For more complex mappings, runsc continues to fall back to the existing
newuidmap/newgidmap mechanism.