fix(native-sidecar): close remaining guest-reachable fatal paths#1811
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Review found the cross-tenant crash was narrowed, not closed: - stdio.rs: the event_ready branch called poll_event_wire(..).await? with no guard, and that reaches the SAME process-event pump the notify branch guards. Both run in one select!, so whether a guest errno killed every co-located VM came down to scheduling. Isolate per session here too. - launch.rs: only the shadow-sync write arm tolerated a guest hitting its own budget. mkdir (charged against maxInodeCount) and symlink (charged against both bytes and inodes) still returned a fatal InvalidState, so a guest exhausting its inode limit could still kill the shared sidecar. Also narrows the tolerated set to ENOSPC only. EDQUOT/EFBIG were dead matches that nothing on this path constructs, and they signal HOST disk exhaustion — a real fault that must keep failing loudly, not be downgraded to a skip. Known gap recorded in the helper doc comment: skipping leaves the shadow copy and the kernel VFS divergent without telling the guest. The correct end state is to fail THIS VM with a typed ENOSPC rather than skip the entry.
This was referenced Jul 20, 2026
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This was referenced Jul 20, 2026
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Review found the cross-tenant crash was narrowed, not closed:
stdio.rs: the event_ready branch called poll_event_wire(..).await? with no
guard, and that reaches the SAME process-event pump the notify branch
guards. Both run in one select!, so whether a guest errno killed every
co-located VM came down to scheduling. Isolate per session here too.
launch.rs: only the shadow-sync write arm tolerated a guest hitting its own
budget. mkdir (charged against maxInodeCount) and symlink (charged against
both bytes and inodes) still returned a fatal InvalidState, so a guest
exhausting its inode limit could still kill the shared sidecar.
Also narrows the tolerated set to ENOSPC only. EDQUOT/EFBIG were dead matches
that nothing on this path constructs, and they signal HOST disk exhaustion —
a real fault that must keep failing loudly, not be downgraded to a skip.
Known gap recorded in the helper doc comment: skipping leaves the shadow copy
and the kernel VFS divergent without telling the guest. The correct end state
is to fail THIS VM with a typed ENOSPC rather than skip the entry.