Date: Thu, 5 May 2005 11:11:31 +0200
To: linux-kernel@vger.kernel.org
Subject: Holding ref to /proc/<pid> dentry prevents task being freed
Message-ID: <20050505091131.GA4472@omnius.cs.uct.ac.za>
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From: bmerry@cs.uct.ac.za
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[Please CC me on replies. I'm not subscribed to LKML]

Hi

I'm busy writing a security module that does some very basic ACL stuff
on a per-task basis. If my module obtains and holds a dentry for
/proc/<pid> (via path_lookup), then the task_free_security hook is
never called for that process. Since the module releases the dentry in
task_free_security, this creates a chicken-and-egg problem and neither
the task nor the dentry is ever released. A side-effect is that the
module refcount never drops to 0.

Perhaps the LSM framework needs a hook for a task exiting (transition
to zombie state), in addition to the task_free_security hook? That
would allow resources to be freed from zombies, including these types
of circular references.

Thanks
Bruce

[Please CC me on replies. I'm not subscribed to LKML]
-- 
/--------------------------------------------------------------------\
| Bruce Merry                      | bmerry at cs . uct . ac . za    |
| Proud user of Gentoo GNU/Linux   | http://www.cs.uct.ac.za/~bmerry |
|        Despite the high cost of living, it remains popular.        |
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