linux-kernel - Re: [PATCH] apparmor: remove the "task" arg from may_change_ptraced

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Message-ID: <20130924164442.GB4036@redhat.com>
Date:	Tue, 24 Sep 2013 18:44:42 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Richard Guy Briggs <rgb@...hat.com>
Cc:	John Johansen <john.johansen@...onical.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] apparmor: remove the "task" arg from
	may_change_ptraced_domain()

On 09/23, Richard Guy Briggs wrote:
>
> On Mon, Sep 16, 2013 at 04:20:35PM +0200, Oleg Nesterov wrote:
> > Unless task == current ptrace_parent(task) is not safe even under
> > rcu_read_lock() and most of the current users are not right.
>
> Could you point to an explanation of this?

If this task exits before rcu_read_lock() ->parent can point to the
already freed/reused memory.

(in the long term we should probably clear
 ->parent/real_parent/group_leader/more in __unhash_process(), but
 lets not discuss this right now ;)

> (Did you send a patch to fix the selinux hook?)

No, sorry, I was sick. Will do.

> Acked-by: Richard Guy Briggs <rgb@...hat.com>

Thanks!

Oleg.

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