On Thu, 2019-12-12 at 13:59 -0800, Lakshmi Ramasubramanian wrote: > 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. > > I think you want to test ima_process_keys before taking the lock and > > again immediately afterward taking the lock, before setting it. Then > > the comment would match the code. > > > > Shouldn't ima_process_keys be defined as static to limit the scope to > > this file? > > > > Mimi > > > > 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. My concern is with the last sentence "Since ima_process_keys is set to true above, any new key will be processed immediately and not queued." It's unlikely, but possible, that a second process will wait for the ima_keys_mutex. Either we remove this sentence or move setting ima_process_keys to after taking the lock. Mimi
