netdev - Re: [PATCH] net: thunderbolt: Fix error handling in tbnet

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Message-ID: <Y3IT7aiOOe2b3Qhy@black.fi.intel.com>
Date:   Mon, 14 Nov 2022 12:09:49 +0200
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Yuan Can <yuancan@...wei.com>
Cc:     michael.jamet@...el.com, YehezkelShB@...il.com,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, andriy.shevchenko@...ux.intel.com,
        amir.jer.levy@...el.com, netdev@...r.kernel.org
Subject: Re: [PATCH] net: thunderbolt: Fix error handling in tbnet_init()

Hi,

On Mon, Nov 14, 2022 at 08:19:36AM +0000, Yuan Can wrote:
> A problem about insmod thunderbolt-net failed is triggered with following
> log given while lsmod does not show thunderbolt_net:
> 
>  insmod: ERROR: could not insert module thunderbolt-net.ko: File exists
> 
> The reason is that tbnet_init() returns tb_register_service_driver()
> directly without checking its return value, if tb_register_service_driver()
> failed, it returns without removing property directory, resulting the
> property directory can never be created later.
> 
>  tbnet_init()
>    tb_register_property_dir() # register property directory
>    tb_register_service_driver()
>      driver_register()
>        bus_add_driver()
>          priv = kzalloc(...) # OOM happened
>    # return without remove property directory
> 
> Fix by remove property directory when tb_register_service_driver() returns
> error.
> 
> Fixes: e69b6c02b4c3 ("net: Add support for networking over Thunderbolt cable")
> Signed-off-by: Yuan Can <yuancan@...wei.com>
> ---
>  drivers/net/thunderbolt.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/thunderbolt.c b/drivers/net/thunderbolt.c
> index 83fcaeb2ac5e..fe6a9881cc75 100644
> --- a/drivers/net/thunderbolt.c
> +++ b/drivers/net/thunderbolt.c
> @@ -1396,7 +1396,14 @@ static int __init tbnet_init(void)
>  		return ret;
>  	}
>  
> -	return tb_register_service_driver(&tbnet_driver);
> +	ret = tb_register_service_driver(&tbnet_driver);
> +	if (ret) {
> +		tb_unregister_property_dir("network", tbnet_dir);
> +		tb_property_free_dir(tbnet_dir);
> +		return ret;
> +	}
> +
> +	return 0;

Okay but I suggest that you make it like:

	ret = tb_register_property_dir("network", tbnet_dir);
	if (ret)
		goto err_free_dir;

	ret = tb_register_service_driver(&tbnet_driver);
	if (ret)
		goto err_unregister;

	return 0;

err_unregister:
	tb_unregister_property_dir("network", tbnet_dir);
err_free_dir:
	tb_property_free_dir(tbnet_dir);

	return ret;

}