Holding ref to /proc/<pid> dentry prevents task being freed

[bmerry@cs.uct.ac.za]

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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]
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| Bruce Merry                      | bmerry at cs . uct . ac . za    |
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