linux-kernel - Re: [PATCH 4/8] cgroup: deactivate CSS's and mark cgroup dead before invoking ->pre

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]

Message-ID: <20121031212359.GC5286@dhcp22.suse.cz>
Date:	Wed, 31 Oct 2012 22:23:59 +0100
From:	Michal Hocko <mhocko@...e.cz>
To:	Tejun Heo <tj@...nel.org>
Cc:	lizefan@...wei.com, hannes@...xchg.org, bsingharora@...il.com,
	kamezawa.hiroyu@...fujitsu.com,
	containers@...ts.linux-foundation.org, cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org, Glauber Costa <glommer@...allels.com>
Subject: Re: [PATCH 4/8] cgroup: deactivate CSS's and mark cgroup dead before
 invoking ->pre_destroy()

On Wed 31-10-12 12:44:06, Tejun Heo wrote:
[...]
> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> index f22e3cd..66204a6 100644
> --- a/kernel/cgroup.c
> +++ b/kernel/cgroup.c
[...]
> @@ -4122,13 +4079,30 @@ static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
>  	}
>  	prepare_to_wait(&cgroup_rmdir_waitq, &wait, TASK_INTERRUPTIBLE);
>  
> -	/* block new css_tryget() by deactivating refcnt */
> +	/*
> +	 * Block new css_tryget() by deactivating refcnt and mark @cgrp
> +	 * removed.  This makes future css_tryget() and child creation
> +	 * attempts fail thus maintaining the removal conditions verified
> +	 * above.
> +	 */
>  	for_each_subsys(cgrp->root, ss) {
>  		struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
>  
>  		WARN_ON(atomic_read(&css->refcnt) < 0);
>  		atomic_add(CSS_DEACT_BIAS, &css->refcnt);
>  	}
> +	set_bit(CGRP_REMOVED, &cgrp->flags);
> +
> +	/*
> +	 * Tell subsystems to initate destruction.  pre_destroy() should be
> +	 * called with cgroup_mutex unlocked.  See 3fa59dfbc3 ("cgroup: fix
> +	 * potential deadlock in pre_destroy") for details.
> +	 */
> +	mutex_unlock(&cgroup_mutex);
> +	for_each_subsys(cgrp->root, ss)
> +		if (ss->pre_destroy)
> +			WARN_ON_ONCE(ss->pre_destroy(cgrp));

Do you think that BUG_ON would be too harsh?

-- 
Michal Hocko
SUSE Labs
--
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/