Re: [Q] eCryptFS race window?

From: Michael Halcrow
Date: Tue May 20 2008 - 14:26:01 EST

On Tue, May 20, 2008 at 09:03:21PM +0400, Cyrill Gorcunov wrote:
> it seems there is a few potential race window in eCryptFS which I
> was trying to fix but it requires more deeper eCrypFS knowledge that
> have (at least only by understanding eCryptFS in big picture it is
> possible to fix this problem by elegant path). So what is the
> problem - the procedures
> ecryptfs_miscdev_poll
> ecryptfs_miscdev_read
> does take ecryptfs_daemon_hash_mux mutex and then daemon->mux _but_
> releases them not in exactly backward order as it should. My patches
> (not in mainline but you saw them) was screwed up 'cause
> mutex_is_locked could release mutex acquired by another process and
> that is wrong. But I've a hope that I'm simply *wrong* about this
> possible races ;) Take a look please.

I cannot find an execution path whereby one of the two must re-acquire
ecryptfs_daemon_hash_mux in order to release daemon->mux, so I do not
think we will ever have deadlock between those two functions.

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