From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f180.google.com (mail-wi0-f180.google.com [209.85.212.180]) by kanga.kvack.org (Postfix) with ESMTP id 823C16B0069 for ; Thu, 20 Nov 2014 10:03:25 -0500 (EST) Received: by mail-wi0-f180.google.com with SMTP id n3so5677465wiv.7 for ; Thu, 20 Nov 2014 07:03:25 -0800 (PST) Received: from mail-wg0-x233.google.com (mail-wg0-x233.google.com. [2a00:1450:400c:c00::233]) by mx.google.com with ESMTPS id dj6si3650134wjc.151.2014.11.20.07.03.24 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Thu, 20 Nov 2014 07:03:24 -0800 (PST) Received: by mail-wg0-f51.google.com with SMTP id k14so3962740wgh.10 for ; Thu, 20 Nov 2014 07:03:24 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <546DFFA1.4030700@redhat.com> References: <502D42E5.7090403@redhat.com> <20120822032057.GA30871@google.com> <50345232.4090002@redhat.com> <20130603195003.GA31275@evergreen.ssec.wisc.edu> <20141114163053.GA6547@cosmos.ssec.wisc.edu> <20141117160212.b86d031e1870601240b0131d@linux-foundation.org> <20141118014135.GA17252@cosmos.ssec.wisc.edu> <546AB1F5.6030306@redhat.com> <20141118121936.07b02545a0684b2cc839a10c@linux-foundation.org> <546BDB29.9050403@suse.cz> <546CC0CD.40906@suse.cz> <546DFFA1.4030700@redhat.com> Date: Thu, 20 Nov 2014 19:03:24 +0400 Message-ID: Subject: Re: [PATCH] Repeated fork() causes SLAB to grow without bound From: Konstantin Khlebnikov Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Rik van Riel Cc: Michel Lespinasse , Vlastimil Babka , Andrew Morton , Hugh Dickins , Andrea Arcangeli , Linux Kernel Mailing List , "linux-mm@kvack.org" , Tim Hartrick , Michal Hocko On Thu, Nov 20, 2014 at 5:50 PM, Rik van Riel 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 > > iQEcBAEBAgAGBQJUbf+hAAoJEM553pKExN6DxhQH/1QL+9GdhaSx7EQnRcbDRcHi > GuEfMU0g9Kv4ad+oPSQnH/L7vJMJAYeh5ZJGH+rOykWHp3sGReqDZOnzpXRAe11z > 1cSC1BJsndzrv9wX8niFpuKpYbF0IP+ckv3qaEzWtm5yCRyhHVZfr6b794Y4K9jF > z2EPPu1vAAldbkx1VlYTwofBA5lESL5UmrFvH4ouI7BeWYSEe6BgVCbvK+K5fANT > ketdA5R08xyUAcXDa+28qpBYkdWnxNhwqseDoXCW8SOFNwWbLDI6GRfrsCNku13i > Gi41h3uEuIAGDf+AU/GMjiymgwutCOGq+cfZlszELaRvHmDpNGYdPv1llghNg7Q= > =Vk+H > -----END PGP SIGNATURE----- -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org