From: Minchan Kim <minchan@kernel.org>
To: Michal Hocko <mhocko@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
linux-api@vger.kernel.org, Johannes Weiner <hannes@cmpxchg.org>,
Tim Murray <timmurray@google.com>,
Joel Fernandes <joel@joelfernandes.org>,
Suren Baghdasaryan <surenb@google.com>,
Daniel Colascione <dancol@google.com>,
Shakeel Butt <shakeelb@google.com>,
Sonny Rao <sonnyrao@google.com>,
Brian Geffon <bgeffon@google.com>,
jannh@google.com, oleg@redhat.com, christian@brauner.io,
oleksandr@redhat.com, hdanton@sina.com, lizeb@google.com
Subject: Re: [PATCH v2 4/5] mm: introduce MADV_PAGEOUT
Date: Thu, 20 Jun 2019 19:32:15 +0900 [thread overview]
Message-ID: <20190620103215.GF105727@google.com> (raw)
In-Reply-To: <20190620092209.GD12083@dhcp22.suse.cz>
On Thu, Jun 20, 2019 at 11:22:09AM +0200, Michal Hocko wrote:
> On Thu 20-06-19 17:40:40, Minchan Kim wrote:
> > > > > Pushing out a shared page cache
> > > > > is possible even now but this interface gives a much easier tool to
> > > > > evict shared state and perform all sorts of timing attacks. Unless I am
> > > > > missing something we should be doing something similar to mincore and
> > > > > ignore shared pages without a writeable access or at least document why
> > > > > we do not care.
> > > >
> > > > I'm not sure IIUC side channel attach. As you mentioned, without this syscall,
> > > > 1. they already can do that simply by memory hogging
> > >
> > > This is way much more harder for practical attacks because the reclaim
> > > logic is not fully under the attackers control. Having a direct tool to
> > > reclaim memory directly then just opens doors to measure the other
> > > consumers of that memory and all sorts of side channel.
> >
> > Not sure it's much more harder. It's really easy on my experience.
> > Just creating new memory hogger and consume memory step by step until
> > you newly allocated pages will be reclaimed.
>
> You can contain an untrusted application into a memcg and it will only
> reclaim its own working set.
>
> > > > 2. If we need fix MADV_PAGEOUT, that means we need to fix MADV_DONTNEED, too?
> > >
> > > nope because MADV_DONTNEED doesn't unmap from other processes.
> >
> > Hmm, I don't understand. MADV_PAGEOUT doesn't unmap from other
> > processes, either.
>
> Either I am confused or missing something. shrink_page_list does
> try_to_unmap and that unmaps from all processes, right?
You don't miss it. It seems now I undetstand what you pointed out.
What you meant is attacker can see what page was faulting-in from other processes
via measuring access delay from his address space and MADV_PAGEOUT makes it more
easiler. Thus, it's an issue regardless of recent mincore fix. Right?
Then, okay, I will add can_do_mincore similar check for the MADV_PAGEOUT syscall
if others have different ideas.
Thanks.
next prev parent reply other threads:[~2019-06-20 10:32 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-10 11:12 [PATCH v2 0/5] Introduce MADV_COLD and MADV_PAGEOUT Minchan Kim
2019-06-10 11:12 ` [PATCH v2 1/5] mm: introduce MADV_COLD Minchan Kim
2019-06-19 12:56 ` Michal Hocko
2019-06-20 0:06 ` Minchan Kim
2019-06-20 7:08 ` Michal Hocko
2019-06-20 8:44 ` Minchan Kim
2019-06-10 11:12 ` [PATCH v2 2/5] mm: change PAGEREF_RECLAIM_CLEAN with PAGE_REFRECLAIM Minchan Kim
2019-06-19 13:09 ` Michal Hocko
2019-06-10 11:12 ` [PATCH v2 3/5] mm: account nr_isolated_xxx in [isolate|putback]_lru_page Minchan Kim
2019-06-10 11:12 ` [PATCH v2 4/5] mm: introduce MADV_PAGEOUT Minchan Kim
2019-06-19 13:24 ` Michal Hocko
2019-06-20 4:16 ` Minchan Kim
2019-06-20 7:04 ` Michal Hocko
2019-06-20 8:40 ` Minchan Kim
2019-06-20 9:22 ` Michal Hocko
2019-06-20 10:32 ` Minchan Kim [this message]
2019-06-20 10:55 ` Michal Hocko
2019-06-10 11:12 ` [PATCH v2 5/5] mm: factor out pmd young/dirty bit handling and THP split Minchan Kim
2019-06-10 18:03 ` [PATCH v2 0/5] Introduce MADV_COLD and MADV_PAGEOUT Dave Hansen
2019-06-13 4:51 ` Minchan Kim
2019-06-12 10:59 ` Pavel Machek
2019-06-12 11:19 ` Oleksandr Natalenko
2019-06-12 11:37 ` Pavel Machek
2019-06-19 12:27 ` Michal Hocko
2019-06-19 23:42 ` Minchan Kim
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