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Message-ID: <1512053826.26048.8.camel@hellion.org.uk>
Date: Thu, 30 Nov 2017 14:57:06 +0000
From: Ian Campbell <ijc@...lion.org.uk>
To: Salvatore Mesoraca <s.mesoraca16@...il.com>, Solar Designer
<solar@...nwall.com>
Cc: David Laight <David.Laight@...lab.com>, Alan Cox
<gnomes@...rguk.ukuu.org.uk>, "linux-kernel@...r.kernel.org"
<linux-kernel@...r.kernel.org>, Kernel Hardening
<kernel-hardening@...ts.openwall.com>, "linux-fsdevel@...r.kernel.org"
<linux-fsdevel@...r.kernel.org>, Alexander Viro <viro@...iv.linux.org.uk>,
Jann Horn <jannh@...gle.com>, Kees Cook <keescook@...omium.org>, "Eric W.
Biederman" <ebiederm@...ssion.com>
Subject: Re: Re: [PATCH v3 2/2] Protected O_CREAT open in
sticky directories
On Thu, 2017-11-30 at 15:39 +0100, Salvatore Mesoraca wrote:
> 2017-11-27 1:26 GMT+01:00 Solar Designer <solar@...nwall.com>:
> > On Fri, Nov 24, 2017 at 12:43:47PM +0100, Salvatore Mesoraca wrote:
> > > 2017-11-24 11:53 GMT+01:00 David Laight <David.Laight@...lab.com>
> > > :
> > > > From: Alan Cox
> > > > > Sent: 22 November 2017 16:52
> > > > >
> > > > > On Wed, 22 Nov 2017 09:01:46 +0100 Salvatore Mesoraca <s.meso
> > > > > raca16@...il.com> wrote:
> > > > >
> > > > > > Disallows O_CREAT open missing the O_EXCL flag, in world or
> > > > > > group writable directories, even if the file doesn't exist
> > > > > > yet.
> > > > > > With few exceptions (e.g. shared lock files based on
> > > > > > flock())
> >
> > Why would "shared lock files based on flock()" need O_CREAT without
> > O_EXCL? Where specifically are they currently used that way?
>
> I don't think that they *need* to act like this, but this is how
> util-linux's flock(1) currently works.
> And it doesn't seem an unreasonable behavior from their perspective,
I thought that too, specifically I reasoned that using O_EXCL would
defeat the purpose of the _shared_ flock(), wouldn't it?
Ian.
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