Subject: Re: [RFC v2 00/10] snet: Security for NETwork syscalls

From: Samir Bellabes <[email-masked]>
Date: Sat, 06 Mar 2010 19:47:56 +0100

Tetsuo Handa <[email-masked]> writes:

> Regarding [RFC v2 09/10] snet: introduce snet_ticket
> +enum snet_verdict snet_ticket_check(struct snet_info *info)
> +{
> +       struct snet_ticket *st = NULL;
> +       unsigned int h = 0, verdict = SNET_VERDICT_NONE;
> +       struct list_head *l = NULL;
> +       struct snet_task_security *tsec = NULL;
> +
> +       if (snet_ticket_mode == SNET_TICKET_OFF)
> +               goto out;
> +
> +       tsec = (struct snet_task_security*) current_security();
> +
> +       h = jhash_2words(info->syscall, info->protocol, 0) % HSIZE;
> +       l = &tsec->hash[h];
> +
> +       read_lock_bh(&tsec->lock);
>
> Credentials are allocated for copy-on-write basis.
> Sharing "tsec" among multiple "struct task_struct" is what you intended?

No, there is no shared "tsec".
snet_ticket_check() is called from the process context. So "tsec" is
a pointer to the "void *security" pointer from its own "struct
task_struct".

every task_struct have a "tsec" allocated to its "void *security"
pointer. 

I will take a second look on how to access the credentials COW.

> Regards.

Tetsuo, thank you again for reviewing.
sam