linux-kernel - Re: [RFC PATCH 2/2] capabilities: allow nice if we are privileged

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Date:	Wed, 24 Jul 2013 01:07:53 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Serge Hallyn <serge.hallyn@...ntu.com>
Cc:	containers@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 2/2] capabilities: allow nice if we are privileged

Serge Hallyn <serge.hallyn@...ntu.com> writes:

> We allow task A to change B's nice level if it has a supserset of
> B's privileges, or of it has CAP_SYS_NICE.  Also allow it if A has
> CAP_SYS_NICE with respect to B - meaning it is root in the same
> namespace, or it created B's namespace.

This patch looks good to me.

We already have this logic elsewhere in the kernel so I don't expect
this will make things worse.

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

> Signed-off-by: Serge Hallyn <serge.hallyn@...onical.com>
> ---
>  security/commoncap.c |    8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/security/commoncap.c b/security/commoncap.c
> index d78b003..ef98b56 100644
> --- a/security/commoncap.c
> +++ b/security/commoncap.c
> @@ -768,16 +768,16 @@ int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)
>   */
>  static int cap_safe_nice(struct task_struct *p)
>  {
> -	int is_subset;
> +	int is_subset, ret = 0;
>  
>  	rcu_read_lock();
>  	is_subset = cap_issubset(__task_cred(p)->cap_permitted,
>  				 current_cred()->cap_permitted);
> +	if (!is_subset && !ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE))
> +		ret = -EPERM;
>  	rcu_read_unlock();
>  
> -	if (!is_subset && !capable(CAP_SYS_NICE))
> -		return -EPERM;
> -	return 0;
> +	return ret;
>  }
>  
>  /**
--
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