containerd overlaybd: integer overflow loading LSMT index from an untrusted image blob

Impact

overlaybd through 1.0.18 computes index_bytes while loading an LSMT index without overflow checking, and the overflowed size leads to out-of-bounds heap access. The input is an overlaybd blob pulled from a registry, so whoever controls an image controls the data. The record scores it network-reachable with no authentication, scope-changed, availability-only impact - a crash of the overlaybd service rather than a demonstrated code-execution path. On a GPU fleet that uses overlaybd for accelerated image pulls, the service is shared by every container on the node, so one tenant's malicious or mirrored image can take image mounts down for co-tenants on the same host. Nodes running plain overlayfs snapshotting are unaffected.

Who can reach it

Anyone who can get an overlaybd-formatted blob onto a registry the node pulls from - a tenant pushing their own image, or a compromised or typo-squatted upstream. No authentication to the node is needed; the scenario in the record involves multiple overlaybd-backed containers on the host.

What to do

Update overlaybd past 1.0.18 to a build containing the two fix commits linked in the record and restart the overlaybd service and snapshotter on each node; running containers with mounted overlaybd devices will need to be recreated. If you cannot patch promptly, restrict pulls to a registry you control and admission-gate image sources, or switch the affected node pools back to the default overlayfs snapshotter.

References

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