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Date:      Fri, 15 May 2020 17:06:27 +0200
From:      Arne Steinkamm <freebsd-hackers@Steinkamm.COM>
To:        Diane Bruce <db@db.net>
Cc:        "Rodney W. Grimes" <freebsd-rwg@gndrsh.dnsmgr.net>, Arne Steinkamm <arne@steinkamm.com>, FreeBSD Hackers <freebsd-hackers@freebsd.org>, freebsd-arch@freebsd.org
Subject:   Re: [HEADSUP] Disallowing read() of a directory fd
Message-ID:  <20200515150627.GY82984@trajan.stk.cx>
In-Reply-To: <20200515144815.GA8265@night.db.net>
References:  <e5a21dd4-6c53-2dca-8fa8-387e2532b7c8@freebsd.org> <202005151247.04FClhsD086497@gndrsh.dnsmgr.net> <20200515144815.GA8265@night.db.net>

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On Fri, May 15, 2020 at 10:48:15AM -0400, Diane Bruce wrote:
> All I have to say on this noisy bikeshed is, let's resurrect the mkdir
> bug of V7 because it's tradition and the BSD way and history and stuff.
> (I only expect a few of you to remember this one.)

Oh, this "bug" was alive until Sys V 3.2 times...

Implementing mkdir as library function without a syscall wasn't a good idea.
ken and dmr saw no reason to implement mkdir as atomic operation.
So it was easy, even with a shell script, to jump between the
mknod(2) and the chown(2) to replace the directory node with a symlink to
/etc/passwd.

This was from a todays point of view a stupid mistake. Reading a directory node
is lightyears away from "a stupid mistake".

Make it switchable with a sysctl switch... would be the best of both worlds.

.//. Arne

-- 
Arne Steinkamm         | Home:     Mail: arne<at>steinkamm<dot>com
Tel.: +49.89.21031004  | Gröbenbachweg 13, 82178 Puchheim, GERMANY




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