From: Motohiro Kosaki <Motohiro.Kosaki@us.fujitsu.com>
To: Manfred Spraul <manfred@colorfullife.com>,
Davidlohr Bueso <davidlohr.bueso@hp.com>,
Michael Kerrisk <mtk.manpages@gmail.com>,
"Martin Schwidefsky" <schwidefsky@de.ibm.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Motohiro Kosaki JP <kosaki.motohiro@jp.fujitsu.com>,
"gthelen@google.com" <gthelen@google.com>,
"aswin@hp.com" <aswin@hp.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: RE: [PATCH 4/4] ipc/shm.c: Increase the defaults for SHMALL, SHMMAX.
Date: Tue, 22 Apr 2014 13:17:15 -0700 [thread overview]
Message-ID: <6B2BA408B38BA1478B473C31C3D2074E30989E9D84@SV-EXCHANGE1.Corp.FC.LOCAL> (raw)
In-Reply-To: <1398090397-2397-5-git-send-email-manfred@colorfullife.com>
> -----Original Message-----
> From: Manfred Spraul [mailto:manfred@colorfullife.com]
> Sent: Monday, April 21, 2014 10:27 AM
> To: Davidlohr Bueso; Michael Kerrisk; Martin Schwidefsky
> Cc: LKML; Andrew Morton; KAMEZAWA Hiroyuki; Motohiro Kosaki JP; gthelen@google.com; aswin@hp.com; linux-mm@kvack.org;
> Manfred Spraul
> Subject: [PATCH 4/4] ipc/shm.c: Increase the defaults for SHMALL, SHMMAX.
>
> System V shared memory
>
> a) can be abused to trigger out-of-memory conditions and the standard
> measures against out-of-memory do not work:
>
> - it is not possible to use setrlimit to limit the size of shm segments.
>
> - segments can exist without association with any processes, thus
> the oom-killer is unable to free that memory.
>
> b) is typically used for shared information - today often multiple GB.
> (e.g. database shared buffers)
>
> The current default is a maximum segment size of 32 MB and a maximum total size of 8 GB. This is often too much for a) and not
> enough for b), which means that lots of users must change the defaults.
>
> This patch increases the default limits (nearly) to the maximum, which is perfect for case b). The defaults are used after boot and as
> the initial value for each new namespace.
>
> Admins/distros that need a protection against a) should reduce the limits and/or enable shm_rmid_forced.
>
> Further notes:
> - The patch only changes default, overrides behave as before:
> # sysctl kernel.shmall=33554432
> would recreate the previous limit for SHMMAX (for the current namespace).
>
> - Disabling sysv shm allocation is possible with:
> # sysctl kernel.shmall=0
> (not a new feature, also per-namespace)
>
> - The limits are intentionally set to a value slightly less than ULONG_MAX,
> to avoid triggering overflows in user space apps.
> [not unreasonable, see http://marc.info/?l=linux-mm&m=139638334330127]
>
> Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
> Reported-by: Davidlohr Bueso <davidlohr@hp.com>
> Cc: mtk.manpages@gmail.com
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
next prev parent reply other threads:[~2014-04-22 20:19 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-21 14:26 [PATCH 0/4] ipc/shm.c: increase the limits for SHMMAX, SHMALL Manfred Spraul
2014-04-21 14:26 ` [PATCH 1/4] ipc/shm.c: check for ulong overflows in shmat Manfred Spraul
2014-04-21 14:26 ` [PATCH 2/4] ipc/shm.c: check for overflows of shm_tot Manfred Spraul
2014-04-21 14:26 ` [PATCH 3/4] ipc/shm.c: check for integer overflow during shmget Manfred Spraul
2014-04-21 14:26 ` [PATCH 4/4] ipc/shm.c: Increase the defaults for SHMALL, SHMMAX Manfred Spraul
2014-04-22 18:21 ` Davidlohr Bueso
2014-04-22 18:28 ` Davidlohr Bueso
2014-04-22 20:17 ` Motohiro Kosaki [this message]
2014-04-23 5:01 ` Michael Kerrisk (man-pages)
2014-04-22 18:19 ` [PATCH 3/4] ipc/shm.c: check for integer overflow during shmget Davidlohr Bueso
2014-04-22 20:16 ` Motohiro Kosaki
2014-04-23 4:59 ` Michael Kerrisk (man-pages)
2014-04-22 18:18 ` [PATCH 2/4] ipc/shm.c: check for overflows of shm_tot Davidlohr Bueso
2014-04-22 20:16 ` Motohiro Kosaki
2014-04-23 4:58 ` Michael Kerrisk (man-pages)
2014-04-22 18:18 ` [PATCH 1/4] ipc/shm.c: check for ulong overflows in shmat Davidlohr Bueso
2014-04-22 20:15 ` Motohiro Kosaki
2014-04-23 4:58 ` Michael Kerrisk (man-pages)
2014-04-21 17:25 ` [PATCH 0/4] ipc/shm.c: increase the limits for SHMMAX, SHMALL Davidlohr Bueso
2014-04-22 4:23 ` Manfred Spraul
2014-04-22 18:18 ` Davidlohr Bueso
2014-04-23 2:53 ` [PATCH 5/4] ipc,shm: minor cleanups Davidlohr Bueso
2014-04-23 5:07 ` Michael Kerrisk (man-pages)
2014-04-23 5:25 ` Davidlohr Bueso
2014-04-23 5:28 ` Michael Kerrisk (man-pages)
2014-04-23 22:27 ` Andrew Morton
2014-04-23 22:35 ` Stephen Rothwell
2014-04-24 5:18 ` Michael Kerrisk (man-pages)
2014-04-24 17:21 ` Davidlohr Bueso
2014-04-23 18:18 ` Manfred Spraul
2014-05-02 13:16 ` [PATCH 0/4] ipc/shm.c: increase the limits for SHMMAX, SHMALL Michael Kerrisk (man-pages)
2014-05-06 20:06 ` Davidlohr Bueso
2014-05-06 20:40 ` Michael Kerrisk (man-pages)
2014-05-06 22:08 ` Davidlohr Bueso
2014-05-07 5:27 ` Michael Kerrisk (man-pages)
2014-05-07 18:22 ` Davidlohr Bueso
2014-05-07 19:17 ` [PATCH v2] ipc,shm: document new limits in the uapi header Davidlohr Bueso
2014-05-09 8:44 ` Michael Kerrisk (man-pages)
2014-05-11 20:46 ` Davidlohr Bueso
2014-05-12 7:44 ` Michael Kerrisk (man-pages)
2014-05-13 1:35 ` Davidlohr Bueso
2014-05-13 6:06 ` Michael Kerrisk (man-pages)
2014-05-06 20:43 ` [PATCH 0/4] ipc/shm.c: increase the limits for SHMMAX, SHMALL Davidlohr Bueso
2014-06-03 19:26 ` Davidlohr Bueso
2014-09-23 5:24 ` Michael Kerrisk (man-pages)
2014-09-24 8:02 ` Davidlohr Bueso
-- strict thread matches above, loose matches on Subject: below --
2014-04-19 11:43 Manfred Spraul
2014-04-19 11:43 ` [PATCH 1/4] ipc/shm.c: check for ulong overflows in shmat Manfred Spraul
2014-04-19 11:43 ` [PATCH 2/4] ipc/shm.c: check for overflows of shm_tot Manfred Spraul
2014-04-19 11:43 ` [PATCH 3/4] ipc/shm.c: check for integer overflow during shmget Manfred Spraul
2014-04-19 11:43 ` [PATCH 4/4] ipc/shm.c: Increase the defaults for SHMALL, SHMMAX Manfred Spraul
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=6B2BA408B38BA1478B473C31C3D2074E30989E9D84@SV-EXCHANGE1.Corp.FC.LOCAL \
--to=motohiro.kosaki@us.fujitsu.com \
--cc=akpm@linux-foundation.org \
--cc=aswin@hp.com \
--cc=davidlohr.bueso@hp.com \
--cc=gthelen@google.com \
--cc=kamezawa.hiroyu@jp.fujitsu.com \
--cc=kosaki.motohiro@jp.fujitsu.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=manfred@colorfullife.com \
--cc=mtk.manpages@gmail.com \
--cc=schwidefsky@de.ibm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).