linux-kernel - Re: [PATCH 1/2] pidns: Don't allow new pids after the namespace is dead.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 15 Feb 2011 19:30:28 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Daniel Lezcano <daniel.lezcano@...e.fr>
Cc:	akpm@...ux-foundation.org, containers@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org, xemul@...nvz.org, sukadev@...ibm.com,
	ebiederm@...ssion.com
Subject: Re: [PATCH 1/2] pidns: Don't allow new pids after the namespace is
	dead.

On 02/15, Daniel Lezcano wrote:
>
> In the case of unsharing or joining a pid namespace, it becomes
> possible to attempt to allocate a pid after zap_pid_namespace has
> killed everything in the namespace.  Close the hole for now by simply
> not allowing any of those pid allocations to succeed.

Daniel, please explain more. It seems, a long ago I knew the reason
for this patch, but now I can't recall and can't understand this change.

> --- a/include/linux/pid_namespace.h
> +++ b/include/linux/pid_namespace.h
> @@ -20,6 +20,7 @@ struct pid_namespace {
>  	struct kref kref;
>  	struct pidmap pidmap[PIDMAP_ENTRIES];
>  	int last_pid;
> +	atomic_t dead;

Why atomic_t? It is used as a plain boolean.

And I can't unde

> --- a/kernel/pid.c
> +++ b/kernel/pid.c
> @@ -282,6 +282,10 @@ struct pid *alloc_pid(struct pid_namespace *ns)
>  	struct pid_namespace *tmp;
>  	struct upid *upid;
>  
> +	pid = NULL;
> +	if (atomic_read(&ns->dead))
> +		goto out;
> +

So why this is needed?

If we see ns->dead != 0 we are already killed by zap_pid_ns_processes()
which sets ns->dead = 1.

Oleg.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/