Local service interruption via snapctl argument confusion

Authorization bypass in Canonical snapd allows local users to exhaust system memory by invoking privileged snapctl mount actions. The snapctl authorization parser treats a help flag after the explicit -- option terminator as a help request, allowing a non-root caller to pass the privilege check for a restricted command. Exploitation requires a confined snap with an administrator-approved mount-control connection; repeated mounts can consume memory until host availability is impaired.