fix(sandbox): skip read-only mounts during recursive chown of /sandbox#2341
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fix(sandbox): skip read-only mounts during recursive chown of /sandbox#2341varshaprasad96 wants to merge 1 commit into
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July 17, 2026 05:55
The sandbox supervisor crashed with EROFS when the recursive chown of /sandbox encountered read-only submounts. This is common in gVisor-based Kubernetes deployments where read-only volume mounts are the only way to enforce per-directory immutability (Landlock is unavailable under gVisor). The fix adds two guards to the ownership walk: 1. Mount-boundary detection via st_dev comparison — paths on a different filesystem than /sandbox are skipped entirely, avoiding the chown call on nested read-only mounts. 2. EROFS tolerance — if chown still returns EROFS (e.g. the root mount itself is read-only), the error is logged at debug level and startup continues. Symlink skipping (already present) is preserved and extracted into the recursive walker for consistency. Manually verified on a kind cluster with a read-only PVC mounted at /sandbox/readonly-data: the pod starts successfully, writable paths are owned by the sandbox user, and the read-only mount retains root ownership. Kubernetes e2e test coverage is a separate follow-up. Closes NVIDIA#2294 Signed-off-by: Varsha Prasad Narsing <varshaprasad96@gmail.com>
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Summary
Fix sandbox supervisor crash (
EROFS: Read-only file system) when the recursivechown /sandboxencounters read-only submounts. This is common in gVisor-based Kubernetes deployments where read-only volume mounts enforce per-directory immutability (Landlock is unavailable under gVisor).Related Issue
Closes #2294
Changes
st_devof each path against the root/sandboxdevice — paths on a different filesystem are skipped entirely, avoiding thechowncall on nested read-only mountschownstill returnsEROFS(e.g. the root mount itself is read-only), the error is logged at debug level and startup continueschown_sandbox_home: Split into entry-point (symlink guard + root_dev capture) andchown_recursive(inner walk with st_dev and EROFS guards)chown_recursive_skips_different_deviceandchown_sandbox_home_does_not_chown_across_device_boundary; strengthened existing symlink rejection testTesting
mise run pre-commitpasses (Rust lint/format/clippy clean; unrelated Python proto env issue)/sandbox/readonly-data: pod starts successfully, writable paths owned by sandbox user, read-only mount retains root ownershipChecklist