Re: [RFC v3 21/22] bpf,landlock: Add optional skb pointer in the Landlock context

[Alexei Starovoitov]

On Wed, Sep 14, 2016 at 09:24:14AM +0200, Mickaël Salaün wrote:
> This is a proof of concept to expose optional values that could depend
> of the process access rights.
> 
> There is two dedicated flags: LANDLOCK_FLAG_ACCESS_SKB_READ and
> LANDLOCK_FLAG_ACCESS_SKB_WRITE. Each of them can be activated to access
> eBPF functions manipulating a skb in a read or write way.
> 
> Signed-off-by: Mickaël Salaün <mic@xxxxxxxxxxx>
...
>  /* Handle check flags */
>  #define LANDLOCK_FLAG_FS_DENTRY		(1 << 0)
> @@ -619,12 +621,15 @@ struct landlock_handle {
>   * @args: LSM hook arguments, see include/linux/lsm_hooks.h for there
>   *        description and the LANDLOCK_HOOK* definitions from
>   *        security/landlock/lsm.c for their types.
> + * @opt_skb: optional skb pointer, accessible with the
> + *           LANDLOCK_FLAG_ACCESS_SKB_* flags for network-related hooks.
>   */
>  struct landlock_data {
>  	__u32 hook; /* enum landlock_hook_id */
>  	__u16 origin; /* LANDLOCK_FLAG_ORIGIN_* */
>  	__u16 cookie; /* seccomp RET_LANDLOCK */
>  	__u64 args[6];
> +	__u64 opt_skb;
>  };

missing something here.
This patch doesn't make use of it.
That's something for the future?
How that field will be populated?
Why make it different vs the rest or args[6] ?