linux-kernel - Re: [PATCH v2 3/5] nvme-fabrics: introduce ref counting for nvmf_ctrl

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Message-ID: <342cf4cf-ad14-4fd0-bcab-fe5fcecf4c0a@grimberg.me>
Date: Thu, 7 Mar 2024 12:27:43 +0200
From: Sagi Grimberg <sagi@...mberg.me>
To: Daniel Wagner <dwagner@...e.de>, James Smart <james.smart@...adcom.com>
Cc: Keith Busch <kbusch@...nel.org>, Christoph Hellwig <hch@....de>,
 Hannes Reinecke <hare@...e.de>, linux-nvme@...ts.infradead.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/5] nvme-fabrics: introduce ref counting for
 nvmf_ctrl_options



On 21/02/2024 15:24, Daniel Wagner wrote:
> The FC transport is offloading the connect attempt to a workqueue. When
> the attempt fails the transport is starting to cleanup resources. It is
> possible for user space to trigger a crash because nvmf_ctrl_options are
> exposed to sysfs.
>
> This crash wasn't observed with blktests nvme/041 until now because the
> retry loop was usually trying for several times (e.g. with defaults
> 600s) and the test would trigger the cleanup itself. Though we the
> recent change not retrying to use invalid credentials the crash can be
> easily triggered.
>
> The simplest way to control the life time of nvmf_ctrl_options is by
> using ref counting.

Why do we need a refcount for an object that has the same exact lifetime
as the ctrl itself? It just feels like unneeded complication.