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From: Oleg Nesterov <oleg@redhat.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: linux-mm@kvack.org,
	Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
	David Rientjes <rientjes@google.com>,
	Vladimir Davydov <vdavydov@parallels.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 0/10 -v4] Handle oom bypass more gracefully
Date: Tue, 14 Jun 2016 22:17:40 +0200	[thread overview]
Message-ID: <20160614201740.GA617@redhat.com> (raw)
In-Reply-To: <20160613141324.GK6518@dhcp22.suse.cz>

On 06/13, Michal Hocko wrote:
>
> On Mon 13-06-16 13:23:48, Michal Hocko wrote:
> > On Thu 09-06-16 13:52:07, Michal Hocko wrote:
> > > I would like to explore ways how to remove kthreads (use_mm) special
> > > case. It shouldn't be that hard, we just have to teach the page fault
> > > handler to recognize oom victim mm and enforce EFAULT for kthreads
> > > which have borrowed that mm.
> >
> > So I was trying to come up with solution for this which would require to
> > hook into the pagefault an enforce EFAULT when the mm is being reaped
> > by the oom_repaer. Not hard but then I have checked the current users
> > and none of them is really needing to read from the userspace (aka
> > copy_from_user/get_user). So we actually do not need to do anything
> > special.
>
> As pointed out by Tetsuo [1] vhost does realy on copy_from_user.

Tetsuo, Michal, but do we really care?

I have no idea what vhost does, but obviously this should not lead to kernel
crash or something like this, otherwise it should be fixed. If we are going
to kill the owner of dev->mm anyway, why should we worry about vhost_worker()
which can fail to access this ->mm after that?

So to me this additional patch looks fine, but probably I missed something?

Oleg.

  reply	other threads:[~2016-06-14 20:17 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-09 11:52 [PATCH 0/10 -v4] Handle oom bypass more gracefully Michal Hocko
2016-06-09 11:52 ` [PATCH 01/10] proc, oom: drop bogus task_lock and mm check Michal Hocko
2016-06-09 11:52 ` [PATCH 02/10] proc, oom: drop bogus sighand lock Michal Hocko
2016-06-09 11:52 ` [PATCH 03/10] proc, oom_adj: extract oom_score_adj setting into a helper Michal Hocko
2016-06-09 11:52 ` [PATCH 04/10] mm, oom_adj: make sure processes sharing mm have same view of oom_score_adj Michal Hocko
2016-06-15 15:03   ` Oleg Nesterov
2016-06-09 11:52 ` [PATCH 05/10] mm, oom: skip vforked tasks from being selected Michal Hocko
2016-06-15 14:51   ` Oleg Nesterov
2016-06-16  6:24     ` Michal Hocko
2016-06-09 11:52 ` [PATCH 06/10] mm, oom: kill all tasks sharing the mm Michal Hocko
2016-06-09 11:52 ` [PATCH 07/10] mm, oom: fortify task_will_free_mem Michal Hocko
2016-06-09 13:18   ` Tetsuo Handa
2016-06-09 14:20     ` Michal Hocko
2016-06-11  8:10       ` Tetsuo Handa
2016-06-13 11:27         ` Michal Hocko
2016-06-16 12:54           ` Tetsuo Handa
2016-06-16 14:29             ` Michal Hocko
2016-06-16 15:40               ` Tetsuo Handa
2016-06-16 15:53                 ` Michal Hocko
2016-06-17 11:38                   ` Tetsuo Handa
2016-06-17 12:26                     ` Michal Hocko
2016-06-17 13:12                       ` Tetsuo Handa
2016-06-17 13:29                         ` Michal Hocko
2016-06-09 11:52 ` [PATCH 08/10] mm, oom: task_will_free_mem should skip oom_reaped tasks Michal Hocko
2016-06-17 11:35   ` Tetsuo Handa
2016-06-17 12:56     ` Michal Hocko
2016-06-09 11:52 ` [PATCH 09/10] mm, oom_reaper: do not attempt to reap a task more than twice Michal Hocko
2016-06-15 14:48   ` Oleg Nesterov
2016-06-16  6:28     ` Michal Hocko
2016-06-09 11:52 ` [PATCH 10/10] mm, oom: hide mm which is shared with kthread or global init Michal Hocko
2016-06-09 15:15   ` Tetsuo Handa
2016-06-09 15:41     ` Michal Hocko
2016-06-16 13:15       ` Tetsuo Handa
2016-06-16 13:36         ` Tetsuo Handa
2016-06-15 14:37   ` Oleg Nesterov
2016-06-16  6:31     ` Michal Hocko
2016-06-13 11:23 ` [PATCH 0/10 -v4] Handle oom bypass more gracefully Michal Hocko
2016-06-13 14:13   ` Michal Hocko
2016-06-14 20:17     ` Oleg Nesterov [this message]
2016-06-14 20:44       ` Oleg Nesterov
2016-06-16  6:33       ` Michal Hocko
2016-06-15 15:09 ` Oleg Nesterov
2016-06-16  6:34   ` Michal Hocko

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