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From: Konstantin Khlebnikov <koct9i@gmail.com>
To: Rik van Riel <riel@redhat.com>
Cc: Michel Lespinasse <walken@google.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	Andrew Morton <akpm@linux-foundation.org>,
	Hugh Dickins <hughd@google.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	Tim Hartrick <tim@edgecast.com>, Michal Hocko <mhocko@suse.cz>
Subject: Re: [PATCH] Repeated fork() causes SLAB to grow without bound
Date: Thu, 20 Nov 2014 19:03:24 +0400	[thread overview]
Message-ID: <CALYGNiP_zqAucmN=Gn75Mm2wK1iE6fPNxTsaTRgnUbFbFE7C-g@mail.gmail.com> (raw)
In-Reply-To: <546DFFA1.4030700@redhat.com>

On Thu, Nov 20, 2014 at 5:50 PM, Rik van Riel <riel@redhat.com> wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> On 11/20/2014 09:42 AM, Konstantin Khlebnikov wrote:
>
>> I'm thinking about limitation for reusing anon_vmas which might
>> increase performance without breaking asymptotic estimation of
>> count anon_vma in the worst case. For example this heuristic: allow
>> to reuse only anon_vma with single direct descendant. It seems
>> there will be arount up to two times more anon_vmas but
>> false-aliasing must be much lower.
>
> It may even be possible to not create a child anon_vma for the
> first child a parent forks, but only create a new anon_vma once
> the parent clones a second child (alive at the same time as the
> first child).
>
> That still takes care of things like apache or sendmail, but
> would not create infinite anon_vmas for a task that keeps forking
> itself to infinite depth without calling exec...

But this scheme is still exploitable. Malicious software easily could create
sequence of forks and exits which leads to infinite chain of anon_vmas.

>
> - --
> All rights reversed
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WARNING: multiple messages have this Message-ID (diff)
From: Konstantin Khlebnikov <koct9i@gmail.com>
To: Rik van Riel <riel@redhat.com>
Cc: Michel Lespinasse <walken@google.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	Andrew Morton <akpm@linux-foundation.org>,
	Hugh Dickins <hughd@google.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	Tim Hartrick <tim@edgecast.com>, Michal Hocko <mhocko@suse.cz>
Subject: Re: [PATCH] Repeated fork() causes SLAB to grow without bound
Date: Thu, 20 Nov 2014 19:03:24 +0400	[thread overview]
Message-ID: <CALYGNiP_zqAucmN=Gn75Mm2wK1iE6fPNxTsaTRgnUbFbFE7C-g@mail.gmail.com> (raw)
In-Reply-To: <546DFFA1.4030700@redhat.com>

On Thu, Nov 20, 2014 at 5:50 PM, Rik van Riel <riel@redhat.com> wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> On 11/20/2014 09:42 AM, Konstantin Khlebnikov wrote:
>
>> I'm thinking about limitation for reusing anon_vmas which might
>> increase performance without breaking asymptotic estimation of
>> count anon_vma in the worst case. For example this heuristic: allow
>> to reuse only anon_vma with single direct descendant. It seems
>> there will be arount up to two times more anon_vmas but
>> false-aliasing must be much lower.
>
> It may even be possible to not create a child anon_vma for the
> first child a parent forks, but only create a new anon_vma once
> the parent clones a second child (alive at the same time as the
> first child).
>
> That still takes care of things like apache or sendmail, but
> would not create infinite anon_vmas for a task that keeps forking
> itself to infinite depth without calling exec...

But this scheme is still exploitable. Malicious software easily could create
sequence of forks and exits which leads to infinite chain of anon_vmas.

>
> - --
> All rights reversed
> -----BEGIN PGP SIGNATURE-----
> Version: GnuPG v1
>
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> Gi41h3uEuIAGDf+AU/GMjiymgwutCOGq+cfZlszELaRvHmDpNGYdPv1llghNg7Q=
> =Vk+H
> -----END PGP SIGNATURE-----

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  reply	other threads:[~2014-11-20 15:03 UTC|newest]

Thread overview: 75+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-08-16  2:46 Repeated fork() causes SLAB to grow without bound Daniel Forrest
2012-08-16 18:58 ` Rik van Riel
2012-08-16 18:58   ` Rik van Riel
2012-08-18  0:03   ` Daniel Forrest
2012-08-18  0:03     ` Daniel Forrest
2012-08-18  3:46     ` Rik van Riel
2012-08-18  3:46       ` Rik van Riel
2012-08-18  4:07       ` Daniel Forrest
2012-08-18  4:07         ` Daniel Forrest
2012-08-18  4:10         ` Rik van Riel
2012-08-18  4:10           ` Rik van Riel
2012-08-20  8:00       ` Hugh Dickins
2012-08-20  8:00         ` Hugh Dickins
2012-08-20  9:39         ` Michel Lespinasse
2012-08-20  9:39           ` Michel Lespinasse
2012-08-20 11:11           ` Andi Kleen
2012-08-20 11:11             ` Andi Kleen
2012-08-20 11:17           ` Rik van Riel
2012-08-20 11:17             ` Rik van Riel
2012-08-20 11:53             ` Michel Lespinasse
2012-08-20 11:53               ` Michel Lespinasse
2012-08-20 19:11               ` Michel Lespinasse
2012-08-20 19:11                 ` Michel Lespinasse
2012-08-22  3:20           ` [RFC PATCH] " Michel Lespinasse
2012-08-22  3:20             ` Michel Lespinasse
2012-08-22  3:29             ` Rik van Riel
2012-08-22  3:29               ` Rik van Riel
2013-06-03 19:50               ` Daniel Forrest
2013-06-03 19:50                 ` Daniel Forrest
2013-06-04 10:37                 ` Rik van Riel
2013-06-04 10:37                   ` Rik van Riel
2013-06-05 14:02                   ` Andrea Arcangeli
2013-06-05 14:02                     ` Andrea Arcangeli
2014-11-14 16:30                 ` [PATCH] " Daniel Forrest
2014-11-14 16:30                   ` Daniel Forrest
2014-11-18  0:02                   ` Andrew Morton
2014-11-18  0:02                     ` Andrew Morton
2014-11-18  1:41                     ` Daniel Forrest
2014-11-18  1:41                       ` Daniel Forrest
2014-11-18  2:41                       ` Rik van Riel
2014-11-18  2:41                         ` Rik van Riel
2014-11-18 20:19                         ` Andrew Morton
2014-11-18 20:19                           ` Andrew Morton
2014-11-18 22:15                           ` Konstantin Khlebnikov
2014-11-18 22:15                             ` Konstantin Khlebnikov
2014-11-18 23:02                             ` Konstantin Khlebnikov
2014-11-18 23:50                               ` Vlastimil Babka
2014-11-18 23:50                                 ` Vlastimil Babka
2014-11-19 14:36                                 ` Konstantin Khlebnikov
2014-11-19 14:36                                   ` Konstantin Khlebnikov
2014-11-19 16:09                                   ` Vlastimil Babka
2014-11-19 16:09                                     ` Vlastimil Babka
2014-11-19 16:58                                     ` Konstantin Khlebnikov
2014-11-19 16:58                                       ` Konstantin Khlebnikov
2014-11-19 23:14                                       ` Michel Lespinasse
2014-11-19 23:14                                         ` Michel Lespinasse
2014-11-20 14:42                                         ` Konstantin Khlebnikov
2014-11-20 14:42                                           ` Konstantin Khlebnikov
2014-11-20 14:50                                           ` Rik van Riel
2014-11-20 14:50                                             ` Rik van Riel
2014-11-20 15:03                                             ` Konstantin Khlebnikov [this message]
2014-11-20 15:03                                               ` Konstantin Khlebnikov
2014-11-24  7:09                                               ` Konstantin Khlebnikov
2014-11-25 10:59                                                 ` Michal Hocko
2014-11-25 10:59                                                   ` Michal Hocko
2014-11-25 12:13                                                   ` Konstantin Khlebnikov
2014-11-25 15:00                                                     ` Michal Hocko
2014-11-25 15:00                                                       ` Michal Hocko
2014-11-26 17:35                                                       ` Michal Hocko
2014-11-26 17:35                                                         ` Michal Hocko
2014-12-05 15:44                                                         ` Jerome Marchand
2014-11-20 15:27                                           ` Michel Lespinasse
2014-11-20 15:27                                             ` Michel Lespinasse
2014-11-19  2:48                           ` Rik van Riel
2014-11-19  2:48                             ` Rik van Riel

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