Re: AW: [syzbot] [fs?] possible deadlock in ovl_create_object (2)

["Jörn Engel" <joern@barelysecure.org>]

I added Adarsh Das, who also attempted to fix this bug.

On Sat, Sep 19, 2026 at 07:42:25AM +0000, Richard Weinberger wrote:
> 
> While we're here, maybe it's time to add a decent configfs interface to
> this driver instead of configuring through module parameters.
> That way also multiple instances are possible.

I honestly wonder whether this driver has any production users.  It is
somewhat useful for developers that want to simulate hardware they don't
have.  But beyond that?

Anyway, I have two deeper review questions as well.

One, afaics block2mtd predates overlayfs.  If the bug requires the
interaction of both, it is overlayfs that introduced the bug.  So why do
we fix it by modifying block2mtd?  Is that really the appropriate way to
fix it?

Two, we fix the deadlock by adding a second thread (via workqueue).  But
to keep synchronous behavior we end up blocking until the second thread
has finished.  Does the blocking behavior recreate a circular dependency
and therefore a deadlock?  If not, why not?

Jörn

--
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