linux-kernel - Re: [PATCH] cpuset: fix allocating page cache/slab object on the unallowed node when memory spread is set

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 for Android: free password hash cracker in your pocket

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

Date:	Wed, 21 Jan 2009 02:41:56 -0800
From:	Paul Menage <menage@...gle.com>
To:	miaox@...fujitsu.com
Cc:	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux-Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cpuset: fix allocating page cache/slab object on the 
	unallowed node when memory spread is set

On Wed, Jan 21, 2009 at 12:06 AM, Miao Xie <miaox@...fujitsu.com> wrote:
> The task still allocated the page caches on old node after modifying its
> cpuset's mems when 'memory_spread_page' was set, it is caused by the old
> mem_allowed_list of the task, the current kernel doesn't updates it unless some
> function invokes cpuset_update_task_memory_state(), it is too late sometimes.

Can you give a more concrete example of how the current code can break?

> We must update the mem_allowed_list of the tasks in time.

This is a fairly fundamental change to the way that mems_allowed is
handled - it dates back to fairly early in cpusets' history.

> - * The task_struct fields mems_allowed and mems_generation may only
> - * be accessed in the context of that task, so require no locks.
> + * The task_struct fields mems_allowed may only be accessed in the context
> + * of that task, so require no locks.

This comment is no longer true, since mems_allowed is now being
updated by other processes.

What's to stop a task reading current->mems_allowed and racing with an
update from update_tasks_nodemask() ? Or else, why can that not lead
to badness?

Paul
--
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/