netdev - Re: [PATCH net] hsr: Handle failures in module init

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Date: Thu, 14 Mar 2024 16:56:35 +0100
From: Felix Maurer <fmaurer@...hat.com>
To: Breno Leitao <leitao@...ian.org>
Cc: netdev@...r.kernel.org, davem@...emloft.net, edumazet@...gle.com,
 kuba@...nel.org, pabeni@...hat.com
Subject: Re: [PATCH net] hsr: Handle failures in module init

On 14.03.24 13:59, Breno Leitao wrote:
> On Thu, Mar 14, 2024 at 11:10:52AM +0100, Felix Maurer wrote:
>> A failure during registration of the netdev notifier was not handled at
>> all. A failure during netlink initialization did not unregister the netdev
>> notifier.
>>
>> Handle failures of netdev notifier registration and netlink initialization.
>> Both functions should only return negative values on failure and thereby
>> lead to the hsr module not being loaded.
>>
>> Signed-off-by: Felix Maurer <fmaurer@...hat.com>
>> ---
>>  net/hsr/hsr_main.c | 18 ++++++++++++++----
>>  1 file changed, 14 insertions(+), 4 deletions(-)
>>
>> diff --git a/net/hsr/hsr_main.c b/net/hsr/hsr_main.c
>> index cb83c8feb746..1c4a5b678688 100644
>> --- a/net/hsr/hsr_main.c
>> +++ b/net/hsr/hsr_main.c
>> @@ -148,14 +148,24 @@ static struct notifier_block hsr_nb = {
>>  
>>  static int __init hsr_init(void)
>>  {
>> -	int res;
>> +	int err;
>>  
>>  	BUILD_BUG_ON(sizeof(struct hsr_tag) != HSR_HLEN);
>>  
>> -	register_netdevice_notifier(&hsr_nb);
>> -	res = hsr_netlink_init();
>> +	err = register_netdevice_notifier(&hsr_nb);
>> +	if (err)
>> +		goto out;
> 
> Can't you just 'return err' here? And avoid the `out` label below?
> 
>> +
>> +	err = hsr_netlink_init();
>> +	if (err)
>> +		goto cleanup;
> 
> Same here, you can do something like the following and remove the
> all the labels below, making the function a bit clearer.
> 
> 	if (err) {
> 		unregister_netdevice_notifier(&hsr_nb);
> 		return err;
> 	}

I usually follow the pattern with labels to make sure the cleanup is not
forgotten later when extending the function. But there is likely not
much change in the module init, I'll remove the labels in the next
iteration.

Thanks,
   Felix