Luca Boccassi
301e7cd047
When using hidepid=invisible on procfs, the kernel will check if the gid of the process trying to access /proc is the same as the gid of the process that mounted the /proc instance, or if it has the ptrace capability: https://github.com/torvalds/linux/blob/v5.10/fs/proc/base.c#L723 https://github.com/torvalds/linux/blob/v5.10/fs/proc/root.c#L155 Given we set up the /proc instance as root for system services, The same restriction applies to CAP_SYS_PTRACE, if a process runs with it then hidepid=invisible has no effect. ProtectProc effectively can only be used with User= or DynamicUser=yes, without CAP_SYS_PTRACE. Update the documentation to explicitly state these limitations. Fixes #18997
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