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

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Date:	Thu, 13 Dec 2012 19:32:51 -0800
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	"Serge E. Hallyn" <serge@...lyn.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	containers@...ts.linux-foundation.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andy Lutomirski <luto@...capital.net>,
	linux-security-module@...r.kernel.org
Subject: Re: [RFC][PATCH] Fix cap_capable to only allow owners in the parent user namespace to have caps.

"Serge E. Hallyn" <serge@...lyn.com> writes:

> Quoting Eric W. Biederman (ebiederm@...ssion.com):
>> 
>> Andy Lutomirski pointed out that the current behavior of allowing the
>> owner of a user namespace to have all caps when that owner is not in a
>> parent user namespace is wrong.
>
> To make sure I understand right, the issue is when a uid is mapped
> into multiple namespaces.

Yes.

i.e. uid 1000 in ns1 may own ns2, but uid 1000 in ns3 does not?

I am not certain of your example.

The simple case is:

init_user_ns:
     child_user_ns1 (owned by uid == 0 [in all user namespaces])
           child_user_ns2 (owned by uid == 0 [ in all user namespaces])


root (uid == 0) in child_user_ns2 has all rights over anything in
child_user_ns1.


Thank you for looking.

Eric
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