Messages in this thread | | | Date | Sun, 22 Apr 2018 18:27:38 -0600 | From | Michal Hocko <> | Subject | Re: DOS by unprivileged user |
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On Sun 22-04-18 10:43:00, vcaputo@pengaru.com wrote: > 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.
I am afraid there is none yet. Johannes had some ground work for page cache trashing detection https://marc.info/?i=20170727153010.23347-1-hannes%40cmpxchg.org but there was no version of the patchseries for quite some time and there was no integration into the oom detection which would be non-trivial as well.
I realize this sucks. But the reality is that this is far from trivial to resolve without introducing pre-mature OOM killer invocations. -- Michal Hocko SUSE Labs
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