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Date:   Fri, 24 Nov 2017 10:53:11 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Alan Cox' <>,
        Salvatore Mesoraca <>
CC:     "" <>,
        "Kernel Hardening" <>,
        "" <>,
        "Alexander Viro" <>,
        Jann Horn <>,
        Kees Cook <>,
        Solar Designer <>,
        "Eric W. Biederman" <>
Subject: RE: [PATCH v3 2/2] Protected O_CREAT open in sticky directories

From: Alan Cox
> Sent: 22 November 2017 16:52
> On Wed, 22 Nov 2017 09:01:46 +0100
> Salvatore Mesoraca <> 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())
> Enough exceptions to make it a bad idea.
> Firstly if you care this much *stop* having shared writable directories.
> We have namespaces, you don't need them. You can give every user their
> own /tmp etc.

Looks like a very bad idea to me as well.

Doesn't this stop all shell redirects into a shared /tmp ?
I'm pretty sure most programs use O_CREAT | O_TRUNC for output
files - they'll all stop working.

If there are some directories where you need to force O_EXCL you
need to make it a property of the directory, not the kernel.


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