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

[Lakshmi Ramasubramanian <nramas@linux.microsoft.com>]

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