linux-kernel - Re: [PATCH 4/5] audit: anchor all pid references in the initial pid namespace

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Message-ID: <20131230180600.GD2457@redhat.com>
Date:	Mon, 30 Dec 2013 19:06:00 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Richard Guy Briggs <rgb@...hat.com>
Cc:	linux-audit@...hat.com, linux-kernel@...r.kernel.org,
	Eric Paris <eparis@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	John Johansen <john.johansen@...onical.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [PATCH 4/5] audit: anchor all pid references in the initial
	pid namespace

On 12/23, Richard Guy Briggs wrote:
>
> Store and log all PIDs with reference to the initial PID namespace and
> use the access functions task_pid_nr() and task_tgid_nr() for task->pid
> and task->tgid rather than access them directly.

At first glance this patch looks like a good cleanup, but...

> @@ -429,6 +429,19 @@ static struct audit_entry *audit_data_to_entry(struct audit_rule_data *data,
>  			f->val = 0;
>  		}
>
> +		if ((f->type == AUDIT_PID) || (f->type == AUDIT_PPID)) {
> +			struct pid *pid;
> +			rcu_read_lock();
> +			pid = find_vpid(f->val);
> +			if (!pid) {
> +				rcu_read_unlock();
> +				err = -ESRCH;
> +				goto exit_free;
> +			}
> +			f->val = pid_nr(pid);
> +			rcu_read_unlock();
> +		}

I do not really understand this change, but this doesn't matter, I do
not understand audit.

However, I think this deserves a separate patch with the changelog.

> @@ -278,9 +278,12 @@ static void dump_common_audit_data(struct audit_buffer *ab,
>  	}
>  	case LSM_AUDIT_DATA_TASK:
>  		tsk = a->u.tsk;
> -		if (tsk && tsk->pid) {
> -			audit_log_format(ab, " pid=%d comm=", tsk->pid);
> -			audit_log_untrustedstring(ab, tsk->comm);
> +		if (tsk) {
> +			pid_t pid = task_pid_nr(tsk);
> +			if (pid) {
> +				audit_log_format(ab, " pid=%d comm=", pid);
> +				audit_log_untrustedstring(ab, tsk->comm);

Just curious, is it really possible that a->u.tsk is an idle thread?

Oleg.

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