linux-kernel - Re: [PATCH] lib/kobject: Simplify checking of parameters in kobj_ns_type

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <YqxAJ0JiN7V1uekr@kroah.com>
Date:   Fri, 17 Jun 2022 10:49:43 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     wuchi <wuchi.zero@...il.com>
Cc:     rafael@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] lib/kobject: Simplify checking of parameters in
 kobj_ns_type_register.

On Fri, Jun 17, 2022 at 04:38:32PM +0800, wuchi wrote:
> 1. Merge checking of following code:
>     if (type >= KOBJ_NS_TYPES)
>     ...
>     if (type <= KOBJ_NS_TYPE_NONE)

Why?

> 2. Move the checking of parameters out of critical section, there is
> no need to check that with spinlock.

Why does it matter?


> 
> Signed-off-by: wuchi <wuchi.zero@...il.com>
> ---
>  lib/kobject.c | 14 ++++----------
>  1 file changed, 4 insertions(+), 10 deletions(-)
> 
> diff --git a/lib/kobject.c b/lib/kobject.c
> index 5f0e71ab292c..6a8b009682b8 100644
> --- a/lib/kobject.c
> +++ b/lib/kobject.c
> @@ -996,19 +996,13 @@ static const struct kobj_ns_type_operations *kobj_ns_ops_tbl[KOBJ_NS_TYPES];
>  int kobj_ns_type_register(const struct kobj_ns_type_operations *ops)
>  {
>  	enum kobj_ns_type type = ops->type;
> -	int error;
> -
> -	spin_lock(&kobj_ns_type_lock);
> +	int error = -EBUSY;
>  
> -	error = -EINVAL;
> -	if (type >= KOBJ_NS_TYPES)
> -		goto out;
> +	if (unlikely(type >= KOBJ_NS_TYPES || type <= KOBJ_NS_TYPE_NONE))

Why add unlikely?  Did you measure the performance benifit?  If not,
please never add likely/unlikely.

> +		return -EINVAL;
>  
> -	error = -EINVAL;
> -	if (type <= KOBJ_NS_TYPE_NONE)
> -		goto out;
> +	spin_lock(&kobj_ns_type_lock);
>  
> -	error = -EBUSY;


How did you test this?  What is the benefit?

thanks,

greg k-h