netdev - Re: [PATCH net-next] devlink: keep the instance mutex alive until references are gone

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Date:   Wed, 11 Jan 2023 10:26:16 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     davem@...emloft.net, netdev@...r.kernel.org, edumazet@...gle.com,
        pabeni@...hat.com, jacob.e.keller@...el.com,
        syzbot+d94d214ea473e218fc89@...kaller.appspotmail.com
Subject: Re: [PATCH net-next] devlink: keep the instance mutex alive until
 references are gone

Wed, Jan 11, 2023 at 05:29:08AM CET, kuba@...nel.org wrote:
>The reference needs to keep the instance memory around, but also
>the instance lock must remain valid. Users will take the lock,
>check registration status and release the lock. mutex_destroy()
>etc. belong in the same place as the freeing of the memory.
>
>Unfortunately lockdep_unregister_key() sleeps so we need
>to switch the an rcu_work.
>
>Note that the problem is a bit hard to repro, because
>devlink_pernet_pre_exit() iterates over registered instances.
>AFAIU the instances must get devlink_free()d concurrently with
>the namespace getting deleted for the problem to occur.
>
>Reported-by: syzbot+d94d214ea473e218fc89@...kaller.appspotmail.com
>Fixes: 9053637e0da7 ("devlink: remove the registration guarantee of references")
>Signed-off-by: Jakub Kicinski <kuba@...nel.org>

Reported-by: syzbot+9f0dd863b87113935acf@...kaller.appspotmail.com