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>,
Michal Hocko <mhocko@suse.com>
Subject: Re: [PATCH 4/6] mm, oom: skip vforked tasks from being selected
Date: Mon, 30 May 2016 21:28:57 +0200 [thread overview]
Message-ID: <20160530192856.GA25696@redhat.com> (raw)
In-Reply-To: <1464613556-16708-5-git-send-email-mhocko@kernel.org>
On 05/30, Michal Hocko wrote:
>
> Make sure to not select vforked task as an oom victim by checking
> vfork_done in oom_badness.
I agree, this look like a good change to me... But.
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -176,11 +176,13 @@ unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg,
>
> /*
> * Do not even consider tasks which are explicitly marked oom
> - * unkillable or have been already oom reaped.
> + * unkillable or have been already oom reaped or the are in
> + * the middle of vfork
> */
> adj = (long)p->signal->oom_score_adj;
> if (adj == OOM_SCORE_ADJ_MIN ||
> - test_bit(MMF_OOM_REAPED, &p->mm->flags)) {
> + test_bit(MMF_OOM_REAPED, &p->mm->flags) ||
> + p->vfork_done) {
I don't think we can trust vfork_done != NULL.
copy_process() doesn't disallow CLONE_VFORK without CLONE_VM, so with this patch
it would be trivial to make the exploit which hides a memory hog from oom-killer.
So perhaps we need something like
bool in_vfork(p)
{
return p->vfork_done &&
p->real_parent->mm == mm;
}
task_lock() is not enough if CLONE_VM was used along with CLONE_PARENT... so this
also needs rcu_read_lock() to access ->real_parent.
Or I am totally confused?
Oleg.
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next prev parent reply other threads:[~2016-05-30 19:29 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-30 13:05 [PATCH 0/6 -v2] Handle oom bypass more gracefully Michal Hocko
2016-05-30 13:05 ` [PATCH 1/6] proc, oom: drop bogus task_lock and mm check Michal Hocko
2016-05-30 13:49 ` Vladimir Davydov
2016-05-30 17:43 ` Oleg Nesterov
2016-05-31 7:32 ` Michal Hocko
2016-05-31 22:53 ` Oleg Nesterov
2016-06-01 6:53 ` Michal Hocko
2016-06-01 10:41 ` Tetsuo Handa
2016-06-01 10:48 ` Michal Hocko
2016-05-30 13:05 ` [PATCH 2/6] proc, oom_adj: extract oom_score_adj setting into a helper Michal Hocko
2016-05-30 13:05 ` [PATCH 3/6] mm, oom_adj: make sure processes sharing mm have same view of oom_score_adj Michal Hocko
2016-05-31 7:41 ` Michal Hocko
2016-05-30 13:05 ` [PATCH 4/6] mm, oom: skip vforked tasks from being selected Michal Hocko
2016-05-30 19:28 ` Oleg Nesterov [this message]
2016-05-31 7:42 ` Michal Hocko
2016-05-31 21:43 ` Oleg Nesterov
2016-06-01 7:09 ` Michal Hocko
2016-06-01 14:12 ` Tetsuo Handa
2016-06-01 14:25 ` Michal Hocko
2016-06-02 10:45 ` Tetsuo Handa
2016-06-02 11:20 ` Michal Hocko
2016-06-02 11:31 ` Tetsuo Handa
2016-06-02 12:55 ` Michal Hocko
2016-05-30 13:05 ` [PATCH 5/6] mm, oom: kill all tasks sharing the mm Michal Hocko
2016-05-30 18:18 ` Oleg Nesterov
2016-05-31 7:43 ` Michal Hocko
2016-05-31 21:48 ` Oleg Nesterov
2016-05-30 13:05 ` [PATCH 6/6] mm, oom: fortify task_will_free_mem Michal Hocko
2016-05-30 17:35 ` Oleg Nesterov
2016-05-31 7:46 ` Michal Hocko
2016-05-31 22:29 ` Oleg Nesterov
2016-06-01 7:03 ` Michal Hocko
2016-05-31 15:03 ` Tetsuo Handa
2016-05-31 15:10 ` Michal Hocko
2016-05-31 15:29 ` Tetsuo Handa
2016-06-01 7:25 ` Michal Hocko
2016-06-01 12:04 ` Tetsuo Handa
2016-06-01 12:43 ` Michal Hocko
2016-06-02 14:03 ` [PATCH 7/6] mm, oom: task_will_free_mem should skip oom_reaped tasks Michal Hocko
2016-06-02 15:24 ` Tetsuo Handa
2016-06-02 15:50 ` Michal Hocko
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