linux-kernel - Re: [PATCH 2/2] user namespaces: require cap_set{ug}id for CLONE

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Date:	Fri, 05 Dec 2008 09:14:05 -0800
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	"Serge E. Hallyn" <serue@...ibm.com>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	David Howells <dhowells@...hat.com>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	Dhaval Giani <dhaval@...ux.vnet.ibm.com>,
	James Morris <jmorris@...ei.org>
Subject: Re: [PATCH 2/2] user namespaces: require cap_set{ug}id for CLONE_NEWUSER

"Serge E. Hallyn" <serue@...ibm.com> writes:

> While ideally CLONE_NEWUSER will eventually require no
> privilege, the required permission checks are currently
> not there.  As a result, CLONE_NEWUSER has the same effect
> as a setuid(0)+setgroups(1,"0").  While we already require
> CAP_SYS_ADMIN, requiring CAP_SETUID and CAP_SETGID seems
> appropriate.

Acked-by: "Eric W. Biederman" <ebiederm@...ssion.com>

The patch looks good, and we are likely to need more caps to
actually use it.
 
>
> Signed-off-by: Serge E. Hallyn <serue@...ibm.com>
> ---
>  kernel/fork.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
>
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 1dd8945..e3a85b3 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -1344,7 +1344,8 @@ long do_fork(unsigned long clone_flags,
>  		/* hopefully this check will go away when userns support is
>  		 * complete
>  		 */
> -		if (!capable(CAP_SYS_ADMIN))
> +		if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
> +				!capable(CAP_SETGID))
>  			return -EPERM;
>  	}
>  
> -- 
> 1.5.4.3
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