Re: [PATCH v4 2/2] IMA: Call workqueue functions to measure queued keys

[Lakshmi Ramasubramanian]

On 12/17/2019 6:44 PM, Lakshmi Ramasubramanian wrote:

> > The direct implication of the comment and the lock dance with the
> > temporary list and the processed flag is that stuff can be added to the
> > ima_keys list after you drop the mutex. Your explanation in the prior
> > couple of emails says that nothing can be added because the
> > ima_process_keys flag setting prevents it. If the latter is true, you
> > can simply drop the lock after setting the flag and rely on ima_keys
> > not changing to run it through process_buffer_measurement without
> > needing any of the intermediate list or the processed flag. If the
> > latter isn't true then any key added to ima_keys after the mutex is
> > dropped is never processed.
> >
> > James

One more scenario needs to be taken care - that still doesn't require a 
temp list, but will need a local flag.

Say, two threads race to call ima_process_queued_keys().
Both find ima_process_keys flag is false.
They now race to take to the lock.
Only the 1st one setting the flag to true should process queued keys.

 -lakshmi