From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753482AbeDVRwU (ORCPT ); Sun, 22 Apr 2018 13:52:20 -0400 Received: from shells.gnugeneration.com ([66.240.222.126]:40836 "EHLO shells.gnugeneration.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751683AbeDVRwT (ORCPT ); Sun, 22 Apr 2018 13:52:19 -0400 Date: Sun, 22 Apr 2018 10:43:00 -0700 From: vcaputo@pengaru.com To: Pavel Machek Cc: Ferry Toth , linux-kernel@vger.kernel.org Subject: Re: DOS by unprivileged user Message-ID: <20180422174300.srzhf3veqxfigqhg@shells.gnugeneration.com> References: <9023506.UBh6vynRGa@delfion> <20180422101654.GA26243@amd> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180422101654.GA26243@amd> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Apr 22, 2018 at 12:16:54PM +0200, Pavel Machek wrote: > On Thu 2018-04-19 21:13:35, Ferry Toth wrote: > > It appears any ordinary user can easily create a DOS on linux. > > > > One sure way to reproduce this is to open gitk on the linux kernel repo > > (SIC) on a machine with 8GB RAM 16 GB swap on a HDD with btrfs and quad core > > + hyperthreading. But I will be easy enough to get the same effect with more > > RAM, other fs etc. > > You may want to disable swap. > I run without swap on my laptops, and still observe long periods of thrashing on the road towards OOM. What seems to occur is the active file-backed mappings of executables/libraries become a sort of swap area, repeatedly being discarded and faulted back in as the context switches occur. If there's any good way to prevent this, I'd like to know. Regards, Vito Caputo