Re: [PATCH v2 1/2] IMA: Define workqueue for early boot "key" measurements
From: Lakshmi Ramasubramanian
Date: Thu Dec 12 2019 - 16:59:40 EST
On 12/12/19 1:13 PM, Mimi Zohar wrote:
Looking at this again, something seems off or at least the comment
doesn't match the code.
* To avoid holding the mutex while processing queued keys,
* transfer the queued keys with the mutex held to a temp list,
* release the mutex, and then process the queued keys from
* the temp list.
* Since ima_process_keys is set to true above, any new key will
* be processed immediately and not queued.
Setting ima_process_key before taking the lock won't prevent the race.
ÂI think you want to test ima_process_keys before taking the lock and
again immediately afterward taking the lock, before setting it. ÂThen
the comment would match the code.
Shouldn't ima_process_keys be defined as static to limit the scope to
In IMA hook, ima_process_key is checked without lock. If it is false,
ima_queue_key is called. If the key was queued (by ima_queue_key()) then
the hook defers measurement. Else, it processes it immediately.
In ima_queue_key() function the check for ima_process_key is done after
taking the lock and the key queued if the flag is false.
In ima_process_keys() ima_process_key is set without lock and then the
queued keys are moved to a temp list after taking the lock.
I have reviewed the changes myself and also with a few of my colleagues.
I don't think there is a race condition. Please let me know if you do
see a problem.
I can move the setting of ima_process_key flag inside the lock. But
honestly I don't think that is necessary.
I agree that ima_process_keys should be static since it is used in this
file one. I'll make that change.
I can also move the setting of ima_process_key flag inside the lock
along with the above change.