[PATCH net] hsr: Handle failures in module init

[PATCH net] hsr: Handle failures in module init

[Felix Maurer]

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@redhat.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;
+
+	err = hsr_netlink_init();
+	if (err)
+		goto cleanup;
 
-	return res;
+	return 0;
+
+cleanup:
+	unregister_netdevice_notifier(&hsr_nb);
+out:
+	return err;
 }
 
 static void __exit hsr_exit(void)
-- 
2.44.0

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

[Denis Kirjanov]

On 3/14/24 13:10, 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.
> 
Fixes: f421436a591d3 ("net/hsr: Add support for the High-availability Seamless Redundancy protocol (HSRv0)")
> Signed-off-by: Felix Maurer <fmaurer@redhat.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;
> +
> +	err = hsr_netlink_init();
> +	if (err)
> +		goto cleanup;
>  
> -	return res;
> +	return 0;
> +
> +cleanup:
> +	unregister_netdevice_notifier(&hsr_nb);
> +out:
> +	return err;
>  }
>  
>  static void __exit hsr_exit(void)

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

[Breno Leitao]

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@redhat.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;
	}

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

[Felix Maurer]

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@redhat.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

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

[Simon Horman]

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 <fmaurer@redhat.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.

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.