From: Davidlohr Bueso <davidlohr@hp.com>
To: Manfred Spraul <manfred@colorfullife.com>
Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>,
Michael Kerrisk <mtk.manpages@gmail.com>,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
LKML <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
gthelen@google.com, aswin@hp.com, linux-mm@kvack.org
Subject: Re: [PATCH 0/4] ipc/shm.c: increase the limits for SHMMAX, SHMALL
Date: Tue, 22 Apr 2014 11:18:13 -0700 [thread overview]
Message-ID: <1398190693.2473.7.camel@buesod1.americas.hpqcorp.net> (raw)
In-Reply-To: <5355EEC2.4010304@colorfullife.com>
On Tue, 2014-04-22 at 06:23 +0200, Manfred Spraul wrote:
> On 04/21/2014 07:25 PM, Davidlohr Bueso wrote:
> > On Mon, 2014-04-21 at 16:26 +0200, Manfred Spraul wrote:
> >> Hi all,
> >>
> >> the increase of SHMMAX/SHMALL is now a 4 patch series.
> >> I don't have ideas how to improve it further.
> > Manfred, is there any difference between this set and the one you sent a
> > couple of days ago?
> a) I updated the comments.
> b) the initial set used TASK_SIZE, not I switch to ULONG_MAX-(1L<<24)
>
> >> - Using "0" as a magic value for infinity is even worse, because
> >> right now 0 means 0, i.e. fail all allocations.
> > Sorry but I don't quite get this. Using 0 eliminates the need for all
> > these patches, no? I mean overflows have existed since forever, and
> > taking this route would naturally solve the problem. 0 allocations are a
> > no no anyways.
> No. The patches are required to handle e.g. shmget(,ULONG_MAX,):
> Right now, shmget(,ULONG_MAX,) results in a 0-byte segment.
Ok, I was mixing 'issues' then.
> The risk of using 0 is that it reverses the current behavior:
> Up to now,
> # sysctl kernel.shmall=0
> disables allocations.
> If we define 0 a infinity, then the same configuration would allow
> unlimited allocations.
Right, but as I mentioned, this also contradicts the fact that shmmin
cannot be 0. And again, I don't know who's correct here. Do any
standards mention this? I haven't found anything, and hard-codding
shmmin to 1 seems to be different among OSs, Linux choosing to do so.
This difference must also be commented in the manpage.
That said, I believe that violating this "feature" and forbidding
disabling shm would probably have a more severe penalty (security,
perhaps) for users who rely on this. So while I'm really annoyed that we
"cannot" use 0 because of this, I'm going to give up arguing. I believe
you approach is the safer way of going.
Thanks a lot for looking into this, Manfred.
Davidlohr
next prev parent reply other threads:[~2014-04-22 18:18 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
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 [this message]
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
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