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Date: Sun, 3 Jul 2016 18:47:23 +0200
From: Oleg Nesterov <oleg@redhat.com>
Subject: Re: [RFC PATCH 5/6] vhost, mm: make sure that oom_reaper doesn't
 reap memory read by vhost
Message-ID: <20160703164723.GA30151@redhat.com>
References: <1467365190-24640-1-git-send-email-mhocko@kernel.org>
 <1467365190-24640-6-git-send-email-mhocko@kernel.org>
 <20160703134719.GA28492@redhat.com>
 <20160703140904.GA26908@redhat.com>
 <20160703151829.GA28667@redhat.com>
 <20160703182254-mutt-send-email-mst@redhat.com>
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To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>, linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>, Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>, David Rientjes <rientjes@google.com>, Vladimir Davydov <vdavydov@parallels.com>, Michal Hocko <mhocko@suse.com>

On 07/03, Michael S. Tsirkin wrote:
>
> On Sun, Jul 03, 2016 at 05:18:29PM +0200, Oleg Nesterov wrote:
> >
> > Well, we are going to kill all tasks which share this memory. I mean, ->mm.
> > If "sharing memory with another task" means, say, a file, then this memory
> > won't be unmapped (if shared).
> >
> > So let me ask again... Suppose, say, QEMU does VHOST_SET_OWNER and then we
> > unmap its (anonymous/non-shared) memory. Who else's memory can be corrupted?
>
> As you say, I mean anyone who shares memory with QEMU through a file.

And in this case vhost_worker() reads the anonymous memory of QEMU process,
not the memory which can be shared with another task, correct?

And if QEMU simply crashes, this can't affect anyone who shares memory with
QEMU through a file, yes?

Oleg.

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