linux-kernel - Re: [PATCH 1/4] fs: Implement close-on-fork

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Message-ID: <97f05204-a27c-7cc8-429a-edcf6eebaa11@petrovitsch.priv.at>
Date:   Wed, 22 Apr 2020 16:31:34 +0000
From:   Bernd Petrovitsch <bernd@...rovitsch.priv.at>
To:     "Karstens, Nate" <Nate.Karstens@...min.com>,
        Matthew Wilcox <willy@...radead.org>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        Jeff Layton <jlayton@...nel.org>,
        "J. Bruce Fields" <bfields@...ldses.org>,
        Arnd Bergmann <arnd@...db.de>,
        Richard Henderson <rth@...ddle.net>,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        Matt Turner <mattst88@...il.com>,
        "James E.J. Bottomley" <James.Bottomley@...senpartnership.com>,
        Helge Deller <deller@....de>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "linux-alpha@...r.kernel.org" <linux-alpha@...r.kernel.org>,
        "linux-parisc@...r.kernel.org" <linux-parisc@...r.kernel.org>,
        "sparclinux@...r.kernel.org" <sparclinux@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        David Laight <David.Laight@...lab.com>,
        Changli Gao <xiaosuo@...il.com>
Subject: Re: [PATCH 1/4] fs: Implement close-on-fork

On 22/04/2020 16:02, Karstens, Nate wrote:
>> It's not safe to call system() from a threaded app.  That's all.  It's right there in the DESCRIPTION:
> 
> That is true, but that description is missing from both the Linux man page and the glibc documentation (https://www.gnu.org/software/libc/manual/html_mono/libc.html#Running-a-Command). It seems like a minor point that won't be noticed until it causes a problem, and problems are rare enough they might go unnoticed for a while. We have removed system() from our application, but we're also concerned that libraries we integrate will use system() without our knowledge.

Reimplementing system() is trivial.
LD_LIBRARY_PRELOAD should take care of all system(3) calls.

I wonder it it has some value to add runtime checking for
"multi-threaded" to such lib functions and error out if
yes.

Apart from that, system() is a PITA even on
single/non-threaded apps.

MfG,
	Bernd
-- 
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