From: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: Linux API <linux-api@vger.kernel.org>,
Manfred Spraul <manfred@colorfullife.com>,
Andrew Morton <akpm@linux-foundation.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Kees Cook <keescook@chromium.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Mike Waychison <mikew@google.com>,
LKML <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: Re: shmctl(SHM_STAT) vs. /proc/sysvipc/shm permissions discrepancies
Date: Wed, 20 Dec 2017 17:17:46 +0100 [thread overview]
Message-ID: <CAKgNAkisD7zDRoqJd6Gk1JMCZ8+Huj5QPV04nh2JXHMA+_R0-A@mail.gmail.com> (raw)
In-Reply-To: <20171220092025.GD4831@dhcp22.suse.cz>
Hello Michal,
On 20 December 2017 at 10:20, Michal Hocko <mhocko@kernel.org> wrote:
> On Tue 19-12-17 17:45:40, Michael Kerrisk wrote:
>> But, is
>> there a pressing reason to make the change? (Okay, I guess iterating
>> using *_STAT is nicer than parsing /proc/sysvipc/*.)
>
> The reporter of this issue claims that "Reading /proc/sysvipc/shm is way
> slower than executing the system call." I haven't checked that but I can
> imagine that /proc/sysvipc/shm can take quite some time when there are
> _many_ segments registered.
Yes, that makes sense.
> So they would like to use the syscall but
> the interacting parties do not have compatible permissions.
So, I don't think there is any security issue, since the same info is
available in /proc/sysvipc/*. The only question would be whether
change in the *_STAT behavior might surprise some applications into
behaving differently. I presume the chances of that are low, but if it
was a concert, one could add new shmctl/msgctl/semctl *_STAT_ALL (or
some such) operations that have the desired behavior.
Cheers,
Michael
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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next prev parent reply other threads:[~2017-12-20 16:17 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-19 9:48 shmctl(SHM_STAT) vs. /proc/sysvipc/shm permissions discrepancies Michal Hocko
[not found] ` <20171219094848.GE2787-2MMpYkNvuYDjFM9bn6wA6Q@public.gmane.org>
2017-12-19 16:45 ` Michael Kerrisk (man-pages)
2017-12-20 9:20 ` Michal Hocko
2017-12-20 16:17 ` Michael Kerrisk (man-pages) [this message]
2017-12-21 8:02 ` Michal Hocko
[not found] ` <20171221080203.GZ4831-2MMpYkNvuYDjFM9bn6wA6Q@public.gmane.org>
2017-12-21 8:56 ` Michael Kerrisk (man-pages)
[not found] ` <CAKgNAkjSF9fXhKCxPMp92zftA4Qtq91WBt8L5UR50oQO8HgRxw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-02-12 17:30 ` Davidlohr Bueso
2017-12-20 8:32 ` Dr. Manfred Spraul
[not found] ` <f8745470-b4fb-97ef-d6ab-40b437be181c-nhLOkwUX5cPe2c5cEj3t2g@public.gmane.org>
2017-12-20 8:44 ` Michael Kerrisk (man-pages)
2017-12-20 9:13 ` Michal Hocko
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