Re: [PATCH 0/1] autofs: fix memory leak of waitqueues in autofs_catatonic_mode

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On Mon, Feb 13, 2023 at 12:37:16PM +0800, Ian Kent wrote:
> I was going to Ack the patch but I wondering if we should wait a little
> while and perhaps (probably) include the wake up call change as well.

Hmm, those would be separate patches?

An interesting thing is that the code itself supposes the wake up calls
from autofs_wait_release() and autofs_catatonic_mode() to be related in
some way (see autofs_wait fragment):

	 * wq-> is NULL iff the lock is already released
	 * or the mount has been made catatonic.
	wait_event_killable(wq->queue, wq-> == NULL);
	status = wq->status;

It seems 'the lock is already released' refers to autofs_wait_release()
as there is no alternative except the call to catatonic function where
wq-> is NULL. So apparently the wake up calls should be the same
(although I don't know if autofs_catatonic_mode has some different
behaviour in such case, but probably it doesn't differ here).

It's also strange that autofs_kill_sb() calls autofs_catatonic_mode() and
currently it just decrements the wait_ctr's and it is not clear to me
where the waitqueues are eventually freed in such case. Only if
autofs_wait_release() or autofs_wait() are called? I'm not sure whether
they are definitely called after that or not.

> In any case we need Al to accept it (cc'd).
> Hopefully Al will offer his opinion on the changes too.

It would be very nice if probably Al would make it more clear.

At the moment I think that the leak issue should be fixed with the
currenly discussed patch and the wake up call issue should be fixed like
in [1], but perhaps I'm missing something.

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