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Date:   Mon, 21 Feb 2022 20:54:42 -0800
From:   Jakub Kicinski <kuba@kernel.org>
To:     Niels Dossche <niels.dossche@ugent.be>
Cc:     Jiri Pirko <jiri@nvidia.com>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] devlink: use devlink lock on DEVLINK_CMD_PORT_SPLIT
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On Mon, 21 Feb 2022 14:33:25 +0100 Niels Dossche wrote:
> devlink_nl_cmd_port_split_doit is executed without taking the devlink
> instance lock. This function calls to devlink_port_get_from_info, which
> calls devlink_port_get_from_attrs, which calls
> devlink_port_get_by_index, which accesses devlink->port_list without the
> instance lock taken, while in other places devlink->port_list access
> always happens with the instance lock taken. The documentation in the
> struct also say that the devlink lock protects the port_list.
> 
> The flag for no locking was added after refactoring the code to no
> longer use a global lock.
> 
> Fixes: 2406e7e546b2 ("devlink: Add per devlink instance lock")
> Signed-off-by: Niels Dossche <niels.dossche@ugent.be>

You can't do this, driver will likely try to register ports and try 
to re-acquire the same lock. I have a series queued to fix this by
moving the locking into drivers. I'll send it out this week.