parent: exclude the own UID/GID from the subid ranges - #623
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/etc/subuid and /etc/subgid can contain a range that covers the user's own ID, e.g. `dog:1001:1` for the user `dog` with the UID 1001. The own ID is already mapped to the ID 0 in the user namespace, so such a range makes newuidmap map the same host ID twice. The kernel rejects an overlapping map, and newuidmap fails with "write to uid_map failed: Invalid argument". Remove the own ID from the ranges before the map is built. A range that contains the own ID in the middle is split into two ranges, so no host ID is lost. Signed-off-by: abhinavmir <atg271@gmail.com>
The own UID/GID is silently removed from the subid ranges. An admin cannot see why the container gets fewer sub-IDs than /etc/subuid grants. Print a warning for each range that contains the own ID. The warning names the file, the range, and the own ID, and it says that the own ID is already mapped in the user namespace. The warning appears once per range. `withoutSelfID` stays free of logging: it returns the removed ranges, and the caller prints them. Signed-off-by: abhinavmir <atg271@gmail.com>
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End-to-end on Linux, as a user whose subuid range contains their own UID: Before: newuidmap: write to uid_map failed: Invalid argument. |
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#476