Re: [PATCH v2 1/3] seccomp: Add find_notification helper

[Christian Brauner <christian.brauner@ubuntu.com>]

On Thu, May 28, 2020 at 04:08:56AM -0700, Sargun Dhillon wrote:
> This adds a helper which can iterate through a seccomp_filter to
> find a notification matching an ID. It removes several replicated
> chunks of code.
> 
> Signed-off-by: Sargun Dhillon <sargun@sargun.me>
> Cc: Matt Denton <mpdenton@google.com>
> Cc: Kees Cook <keescook@google.com>,
> Cc: Jann Horn <jannh@google.com>,
> Cc: Robert Sesek <rsesek@google.com>,
> Cc: Chris Palmer <palmer@google.com>
> Cc: Christian Brauner <christian.brauner@ubuntu.com>
> Cc: Tycho Andersen <tycho@tycho.ws>
> ---

A single nit below otherwise:

Acked-by: Christian Brauner <christian.brauner@ubuntu.com>

>  kernel/seccomp.c | 51 ++++++++++++++++++++++++------------------------
>  1 file changed, 25 insertions(+), 26 deletions(-)
> 
> diff --git a/kernel/seccomp.c b/kernel/seccomp.c
> index 55a6184f5990..94ae4c7502cc 100644
> --- a/kernel/seccomp.c
> +++ b/kernel/seccomp.c
> @@ -1021,10 +1021,25 @@ static int seccomp_notify_release(struct inode *inode, struct file *file)
>  	return 0;
>  }
>  
> +/* must be called with notif_lock held */
> +static inline struct seccomp_knotif *
> +find_notification(struct seccomp_filter *filter, u64 id)
> +{
> +	struct seccomp_knotif *cur;
> +
> +	list_for_each_entry(cur, &filter->notif->notifications, list) {
> +		if (cur->id == id)
> +			return cur;
> +	}
> +
> +	return NULL;
> +}
> +
> +
>  static long seccomp_notify_recv(struct seccomp_filter *filter,
>  				void __user *buf)
>  {
> -	struct seccomp_knotif *knotif = NULL, *cur;
> +	struct seccomp_knotif *knotif, *cur;
>  	struct seccomp_notif unotif;
>  	ssize_t ret;
>  
> @@ -1078,14 +1093,8 @@ static long seccomp_notify_recv(struct seccomp_filter *filter,
>  		 * may have died when we released the lock, so we need to make
>  		 * sure it's still around.
>  		 */
> -		knotif = NULL;
>  		mutex_lock(&filter->notify_lock);
> -		list_for_each_entry(cur, &filter->notif->notifications, list) {
> -			if (cur->id == unotif.id) {
> -				knotif = cur;
> -				break;
> -			}
> -		}
> +		knotif = find_notification(filter, unotif.id);
>  
>  		if (knotif) {

Nit: additional \n which isn't present before any of the other new
find_notification() invocations.