linux-kernel - Re: [RFC][PATCH] cgroup: fix race between fork and cgroup freezing

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: <20120312161040.GA23255@google.com>
Date:	Mon, 12 Mar 2012 09:10:40 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Li Zefan <lizf@...fujitsu.com>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Cgroups <cgroups@...r.kernel.org>, Mel Gorman <mgorman@...e.de>,
	David Rientjes <rientjes@...gle.com>,
	缪 勰 <miaox@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC][PATCH] cgroup: fix race between fork and cgroup freezing

Hello,

On Mon, Mar 12, 2012 at 05:02:04PM +0800, Li Zefan wrote:
> - We still need some kind of locking to syncronize fork and the traverser.
> fork side is protected by tasklist_lock, while the traverser takes
> css_set_lock.

Can't we do both after tasklist_lock is released under css_set_lock?

> - After linking the new task to css set list, the task is visible and thus
> can be moved to another cgroup, which makes things more complicated and
> the subsystem callbacks may have to acquire cgroup_mutex.

Hmmm... freezer currently doesn't allow migrating in and out of frozen
cgroup and even when it does callbacks in the migration path should
synchronize against freezer->lock.  I *think* that should be enough
and can't see why this will be simpler or more complex depending on
when fork callback is called.

> - The task_counter subsystem wants to get notified before the new task
> is linked, so it's able to abort the fork.

This one maybe but for this cgroup_fork_callbacks() is already too
late, isn't it?  We better have pre-fork callbacks instead, no?

Thanks.

-- 
tejun
--
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/