Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces

[Eric W. Biederman]

"Serge E. Hallyn" <serge@xxxxxxxxxx> writes:

> Quoting Michael Kerrisk (man-pages) (mtk.manpages@xxxxxxxxx):
>> Hi Eric,
>> 
>> On 07/25/2016 03:18 PM, Eric W. Biederman wrote:
>> >"Michael Kerrisk (man-pages)" <mtk.manpages@xxxxxxxxx> writes:
>> >
>> >>Hi Andrey,
>> >>
>> >>On 07/22/2016 08:25 PM, Andrey Vagin wrote:
>> >>Perhaps add "and the caller does not have CAP_SYS_ADMIN" in the initial
>> >>user namespace"?
>> >
>> >Having looked at that bit of code I don't think capabilities really
>> >have a role to play.
>> 
>> Yes, I caught up with that now. I await to see how this plays out
>> in the next patch version.
>
> Thanks - that had caught my eye but I hadn't had time to look into the
> justification for this.  Hiding this kind of thing indeed seems wrong to
> me, unless there is a really good justification for it, i.e. a way
> to use that info in an exploit.

To avoid breaking checkpoint/restart we need to limit information to the
namespaces the caller is a member of for the user and pid namespaces.

This roughly duplicates the parentage checks in ns_capable.

Conceptually this is the same as limiting .. in a chroot environment.

Eric