linux-kernel - Re: [RFC] ipc: introduce shm_rmid

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Message-ID: <20110704150859.GB6893@redhat.com>
Date:	Mon, 4 Jul 2011 17:08:59 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Vasiliy Kulikov <segoon@...nwall.com>
Cc:	kernel-hardening@...ts.openwall.com,
	Randy Dunlap <rdunlap@...otime.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Serge E. Hallyn" <serge.hallyn@...onical.com>,
	Daniel Lezcano <daniel.lezcano@...e.fr>,
	Tejun Heo <tj@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org
Subject: Re: [RFC] ipc: introduce shm_rmid_forced sysctl

On 06/22, Vasiliy Kulikov wrote:
>
> +void exit_shm(struct task_struct *task)
> +{
> +	struct nsproxy *nsp = task->nsproxy;
> +	struct ipc_namespace *ns;
> +
> +	if (!nsp)
> +		return;
> +	ns = nsp->ipc_ns;
> +	if (!ns || !ns->shm_rmid_forced)

This looks confusing, imho. How it is possible that ->nsproxy or
->ipc_ns is NULL?

> +		return;
> +
> +	/* Destroy all already created segments, but not mapped yet */
> +	down_write(&shm_ids(ns).rw_mutex);
> +	idr_for_each(&shm_ids(ns).ipcs_idr, &shm_try_destroy_current, ns);
>  	up_write(&shm_ids(ns).rw_mutex);

Again, I do not pretend I understand ipc/, but it seems we can check
ns->ipc_ids[].in_use != 0 before the slow path, no?

Oleg.

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