linux-kernel - Re: [PATCH 02/16] core: do security check under task

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Date:	Thu, 19 Nov 2009 08:47:37 +1100 (EST)
From:	James Morris <jmorris@...ei.org>
To:	Jiri Slaby <jslaby@...ell.com>
cc:	jirislaby@...il.com, Ingo Molnar <mingo@...e.hu>,
	nhorman@...driver.com, Stephen Rothwell <sfr@...b.auug.org.au>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	marcin.slusarz@...il.com, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com, Linus Torvalds <torvalds@...ux-foundation.org>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	linux-security-module@...r.kernel.org
Subject: Re: [PATCH 02/16] core: do security check under task_lock

On Wed, 18 Nov 2009, Jiri Slaby wrote:

> Do security_task_setrlimit under task_lock. Other tasks may
> change limits under our hands while we are checking limits
> inside the function. From now on, they can't.
> 

Acked-by: James Morris <jmorris@...ei.org>


> Signed-off-by: Jiri Slaby <jslaby@...ell.com>
> Cc: James Morris <jmorris@...ei.org>
> Cc: Heiko Carstens <heiko.carstens@...ibm.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Ingo Molnar <mingo@...e.hu>
> ---
>  kernel/sys.c |   16 +++++++---------
>  1 files changed, 7 insertions(+), 9 deletions(-)
> 
> diff --git a/kernel/sys.c b/kernel/sys.c
> index 605ab9c..0f86199 100644
> --- a/kernel/sys.c
> +++ b/kernel/sys.c
> @@ -1243,7 +1243,7 @@ int setrlimit(struct task_struct *tsk, unsigned int resource,
>  		struct rlimit *new_rlim)
>  {
>  	struct rlimit *old_rlim;
> -	int retval;
> +	int retval = 0;
>  
>  	if (new_rlim->rlim_cur > new_rlim->rlim_max)
>  		return -EINVAL;
> @@ -1260,10 +1260,6 @@ int setrlimit(struct task_struct *tsk, unsigned int resource,
>  		}
>  	}
>  
> -	retval = security_task_setrlimit(tsk, resource, new_rlim);
> -	if (retval)
> -		goto out;
> -
>  	if (resource == RLIMIT_CPU && new_rlim->rlim_cur == 0) {
>  		/*
>  		 * The caller is asking for an immediate RLIMIT_CPU
> @@ -1276,11 +1272,13 @@ int setrlimit(struct task_struct *tsk, unsigned int resource,
>  
>  	old_rlim = tsk->signal->rlim + resource;
>  	task_lock(tsk->group_leader);
> -	if ((new_rlim->rlim_max <= old_rlim->rlim_max) ||
> -				capable(CAP_SYS_RESOURCE))
> -		*old_rlim = *new_rlim;
> -	else
> +	if ((new_rlim->rlim_max > old_rlim->rlim_max) &&
> +				!capable(CAP_SYS_RESOURCE))
>  		retval = -EPERM;
> +	if (!retval)
> +		retval = security_task_setrlimit(tsk, resource, new_rlim);
> +	if (!retval)
> +		*old_rlim = *new_rlim;
>  	task_unlock(tsk->group_leader);
>  
>  	if (retval || resource != RLIMIT_CPU)
> -- 
> 1.6.4.2
> 

-- 
James Morris
<jmorris@...ei.org>
--
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