linux-kernel - Re: [PATCH 0/7] Initial support for user namespace owned mounts

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Date:	Mon, 20 Jul 2015 13:54:59 -0400
From:	Colin Walters <walters@...bum.org>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Casey Schaufler <casey@...aufler-ca.com>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Seth Forshee <seth.forshee@...onical.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Linux FS Devel <linux-fsdevel@...r.kernel.org>,
	LSM List <linux-security-module@...r.kernel.org>,
	"SELinux-NSA" <selinux@...ho.nsa.gov>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/7] Initial support for user namespace owned mounts

On Thu, Jul 16, 2015, at 12:47 AM, Eric W. Biederman wrote:

> With that said desktop environments have for a long time been
> automatically mounting whichever filesystem you place in your computer,
> so in practice what this is really about is trying to align the kernel
> with how people use filesystems.

There is a large attack surface difference between mounting a device
that someone physically plugged into the computer (and note typically
it's required that the active console be unlocked as well[1]) versus
allowing any "unprivileged" process at any time to do it.

Many server setups use "unprivileged" uids that otherwise wouldn't
be able to exploit bugs in filesystem code.

[1] https://bugzilla.gnome.org/show_bug.cgi?id=653520
"AutomountManager also keeps track of the current session availability
(using the ConsoleKit and gnome-screensaver DBus interfaces) and
inhibits mounting if the current session is locked, or another session
is in use instead."

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