Re: [RFC][PATCH] Fix cap_capable to only allow owners in the parent user namespace to have caps.

[Eric W. Biederman]

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

> Quoting Eric W. Biederman (ebiederm@xxxxxxxxxxxx):

>> A child user namespace having capabilities against processes in it's
>> parent seems totally bizarre and pretty dangerous from a capabilities
>> standpoint.
>
> How would it have them against its parent?

init_user_ns
   userns a --- created by kuid 1
     userns b -- created by kuid 2
        process c in userns b with kuid 1

Serge read the first permisison check in common_cap. 
Think what happens in the above example.

For the rest I understand your concern.

Serge please read and look at the patches I have posted to fix
the issues Andy found with the user namespace tree.  Especially
the fix to commit_creds.

After you have looked at the patches to fix the issues I will
be happy to discuss things further with you.

Eric

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