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Date: Wed, 15 Aug 2012 19:44:26 +0100
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Kees Cook <keescook@chromium.org>
Cc: Oleg Nesterov <oleg@redhat.com>, Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Fengguang Wu <fengguang.wu@intel.com>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: yama_ptrace_access_check(): possible recursive locking detected
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> It sounds like get_task_comm shouldn't have locking at all then? It
> should just do a length-limited copy and make sure there is a trailing
> 0-byte?

It has locking so that it has a consistent state and more importantly it
has an accessor function

Directly accessing it is asking for bugs in future. If you hold the
needed lock then just add an

__get_task_comm() 

method that asserts the lock is held. That way the rest of the behaviour
remains properly encapsulated for when someone changes it.

Alan