linux-kernel - Re: [RFC v2 00/10] snet: Security for NETwork syscalls

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Message-ID: <m2vdd9p9r7.fsf@ssh.synack.fr>
Date:	Sat, 06 Mar 2010 19:47:56 +0100
From:	Samir Bellabes <sam@...ack.fr>
To:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc:	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	netfilter-devel@...r.kernel.org, hadi@...erus.ca, kaber@...sh.net,
	zbr@...emap.net, nhorman@...driver.com, root@...aldomain.pl,
	linux-security-module@...r.kernel.org
Subject: Re: [RFC v2 00/10] snet: Security for NETwork syscalls

Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp> 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
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