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

From: Simon Horman <[email-masked]>
Date: Mon, 18 Mar 2024 13:01:49 +0000

On Thu, Mar 14, 2024 at 04:56:35PM +0100, Felix Maurer wrote:
> 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 <[email-masked]>
> >> ---
> >>  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.

FWIIW, I think the use of labels is the right way to go: it is the
idomatic approach preferred in Networking code.

That said, dropping the out label would be fine by me,
as as simple return nice IMHO.