[Devel] Re: namespaces compatibility list

[Cedric Le Goater]

There's also a Documentation/unshare.txt. Should we update it also ?

> --- /dev/null
> +++ b/Documentation/namespaces/compatibility-list.txt
> @@ -0,0 +1,32 @@
> +	Namespaces compatibility list
> +
> +This document contains the information about the problems user
> +may have when creating tasks living in different namespaces.
> +
> +Here's the summary. This matrix shows the known problems, that
> +occur when tasks share some namespace (the columns) while living
> +in different other namespaces (the raws):

s/raws/rows/

> +
> +	UTS	IPC	VFS	PID	User	Net
> +UTS
> +IPC			 1
> +VFS
> +PID		 1	 1
> +User			 2
> +Net

This is dense but I can't think of a better representation.

> +1. Both the IPC and the PID namespaces provide IDs to address
> +   object inside the kernel. E.g. semaphore with ipcid or
> +   process group with pid.
> +
> +   In both cases, tasks shouldn't try telling this id to some

s/telling/exposing/ ?

> +   other task living in different namespace vid shared filesystem

 .. in a different namespace via a shared filesystem  

> +   or IPC shmem/message. The fact is that this ID is only valid
> +   within the namespace it was obtained in and may refer to some
> +   other object in another namespace.
> +
> +2. Intentionnaly, two equal user ids in different user namespaces
> +   should not be equal from the VFS point of view. In other
> +   words, user 10 in one user namespace shouldn't have the same
> +   access permissions to files, beloging to user 10 in another
> +   namespace. But currently this is not so.
> 
> 

Thanks Pavel,

C.
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