From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f69.google.com (mail-wm0-f69.google.com [74.125.82.69]) by kanga.kvack.org (Postfix) with ESMTP id 4BEBD6B0267 for ; Wed, 1 Jun 2016 10:25:06 -0400 (EDT) Received: by mail-wm0-f69.google.com with SMTP id e3so12716689wme.3 for ; Wed, 01 Jun 2016 07:25:06 -0700 (PDT) Received: from mail-wm0-f52.google.com (mail-wm0-f52.google.com. [74.125.82.52]) by mx.google.com with ESMTPS id l185si43492935wmf.120.2016.06.01.07.25.04 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 01 Jun 2016 07:25:05 -0700 (PDT) Received: by mail-wm0-f52.google.com with SMTP id a136so185192803wme.0 for ; Wed, 01 Jun 2016 07:25:04 -0700 (PDT) Date: Wed, 1 Jun 2016 16:25:03 +0200 From: Michal Hocko Subject: Re: [PATCH 4/6] mm, oom: skip vforked tasks from being selected Message-ID: <20160601142502.GY26601@dhcp22.suse.cz> References: <1464613556-16708-1-git-send-email-mhocko@kernel.org> <1464613556-16708-5-git-send-email-mhocko@kernel.org> <201606012312.BIF26006.MLtFVQSJOHOFOF@I-love.SAKURA.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201606012312.BIF26006.MLtFVQSJOHOFOF@I-love.SAKURA.ne.jp> Sender: owner-linux-mm@kvack.org List-ID: To: Tetsuo Handa Cc: linux-mm@kvack.org, rientjes@google.com, oleg@redhat.com, vdavydov@parallels.com, akpm@linux-foundation.org On Wed 01-06-16 23:12:20, Tetsuo Handa wrote: > Michal Hocko wrote: > > vforked tasks are not really sitting on any memory. They are sharing > > the mm with parent until they exec into a new code. Until then it is > > just pinning the address space. OOM killer will kill the vforked task > > along with its parent but we still can end up selecting vforked task > > when the parent wouldn't be selected. E.g. init doing vfork to launch > > a task or vforked being a child of oom unkillable task with an updated > > oom_score_adj to be killable. > > > > Make sure to not select vforked task as an oom victim by checking > > vfork_done in oom_badness. > > While vfork()ed task cannot modify userspace memory, can't such task > allocate significant amount of kernel memory inside execve() operation > (as demonstrated by CVE-2010-4243 64bit_dos.c )? > > It is possible that killing vfork()ed task releases a lot of memory, > isn't it? I am not familiar with the above CVE but doesn't that allocated memory come after flush_old_exec (and so mm_release)? -- Michal Hocko SUSE Labs -- 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