From: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>
To: Manfred Spraul <manfred@colorfullife.com>
Cc: Davidlohr Bueso <davidlohr.bueso@hp.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>,
Greg Thelen <gthelen@google.com>,
aswin@hp.com, "linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: Re: [PATCH 0/4] ipc/shm.c: increase the limits for SHMMAX, SHMALL
Date: Fri, 2 May 2014 15:16:39 +0200 [thread overview]
Message-ID: <CAKgNAkjuU68hgyMOVGBVoBTOhhGdBytQh6H0ExiLoXfujKyP_w@mail.gmail.com> (raw)
In-Reply-To: <1398090397-2397-1-git-send-email-manfred@colorfullife.com>
Hi Manfred,
On Mon, Apr 21, 2014 at 4:26 PM, Manfred Spraul
<manfred@colorfullife.com> wrote:
> Hi all,
>
> the increase of SHMMAX/SHMALL is now a 4 patch series.
> I don't have ideas how to improve it further.
On the assumption that your patches are heading to mainline, could you
send me a man-pages patch for the changes?
Thanks,
Michael
> The change itself is trivial, the only problem are interger overflows.
> The overflows are not new, but if we make huge values the default,
> then the code should be free from overflows.
>
> SHMMAX:
>
> - shmmem_file_setup places a hard limit on the segment size:
> MAX_LFS_FILESIZE.
>
> On 32-bit, the limit is > 1 TB, i.e. 4 GB-1 byte segments are
> possible. Rounded up to full pages the actual allocated size
> is 0. --> must be fixed, patch 3
>
> - shmat:
> - find_vma_intersection does not handle overflows properly.
> --> must be fixed, patch 1
>
> - the rest is fine, do_mmap_pgoff limits mappings to TASK_SIZE
> and checks for overflows (i.e.: map 2 GB, starting from
> addr=2.5GB fails).
>
> SHMALL:
> - after creating 8192 segments size (1L<<63)-1, shm_tot overflows and
> returns 0. --> must be fixed, patch 2.
>
> User space:
> - Obviuosly, there could be overflows in user space. There is nothing
> we can do, only use values smaller than ULONG_MAX.
> I ended with "ULONG_MAX - 1L<<24":
>
> - TASK_SIZE cannot be used because it is the size of the current
> task. Could be 4G if it's a 32-bit task on a 64-bit kernel.
>
> - The maximum size is not standardized across archs:
> I found TASK_MAX_SIZE, TASK_SIZE_MAX and TASK_SIZE_64.
>
> - Just in case some arch revives a 4G/4G split, nearly
> ULONG_MAX is a valid segment size.
>
> - Using "0" as a magic value for infinity is even worse, because
> right now 0 means 0, i.e. fail all allocations.
>
> Andrew: Could you add it into -akpm and move it towards linux-next?
>
> --
> Manfred
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
next prev parent reply other threads:[~2014-05-02 13:17 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
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 ` Michael Kerrisk (man-pages) [this message]
2014-05-06 20:06 ` [PATCH 0/4] ipc/shm.c: increase the limits for SHMMAX, SHMALL 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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