linux-kernel - Re: [TOMOYO #12 (2.6.28-rc2-mm1) 06/11] Common functions for TOMOYOLinux.

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Date:	Mon, 10 Nov 2008 12:30:01 +0900
From:	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
To:	serue@...ibm.com
Cc:	akpm@...ux-foundation.org, linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org, takedakn@...data.co.jp,
	haradats@...data.co.jp, penguin-kernel@...ove.sakura.ne.jp
Subject: Re: [TOMOYO #12 (2.6.28-rc2-mm1) 06/11] Common functions for TOMOYOLinux.

Hello.

Serge E. Hallyn wrote:
> > I need to clarify reachability of "struct task_struct".
> > 
> > A process inside a virtualized environment cannot reach "struct task_struct"
> > which belongs to outside the virtualized environment.
> > 
> > A process outside virtualized environments can reach "struct task_struct"
> > which belongs to inside virtualized environments, can't it?
> 
> To be precise, there isn't a real 'inside' and 'outside' virtualized
> environements.  Rather pid namespaces are hierarchical.
> 
So, processes which have non-topmost namespace cannot see processes which have
topmost namespace (like chroot()).
Then, it might be preferable if TOMOYO can prevent processes which have
non-topmost namespace from modifying policy information.
Do you think TOMOYO should do "current->nsproxy->pid_ns == &init_pid_ns"
checking like below one?

static bool tomoyo_is_policy_manager(void)
{
	struct tomoyo_policy_manager_entry *ptr;
	const char *exe;
	const struct task_struct *task = current;
	const struct tomoyo_path_info *domainname = tomoyo_domain()->domainname;
	bool found = false;

	if (!tomoyo_policy_loaded)
	        return true;
	if (!tomoyo_manage_by_non_root && (task->cred->uid || task->cred->euid))
	        return false;
	/* Don't allow modifying policy by processes not having init_pid_ns. */
	if (task->nsproxy->pid_ns != &init_pid_ns)
		return false;
	list1_for_each_entry(ptr, &tomoyo_policy_manager_list, list) {
		if (!ptr->is_deleted && ptr->is_domain
		    && !tomoyo_pathcmp(domainname, ptr->manager))
			return true;
	}

> (Taking another look) it looks like In is_select_one() you're doing the
> right thing - you look up the domain of a task based on
> find_task_by_vpid() on a passed-in pid.  Seems correct.
> 
I see, thanks.
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